GIFT   OF 
MICHAEL  REESE 


A   TREATISE    ON   CHEMISTRY 


TEEATISE  ON  CHEMISTRY 


BY 

SIB  H.  E.  KOSCOE  F.E.S.  AND  C.  SCHOKLEMMEE  F.K.S. 


VOLUME  III 

THE  CHEMISTRY  OF  THE  HYDROCARBONS  AND  THEIR  DERIVATIVES, 

OB 

ORGANIC  CHEMISTRY 

PART  IV 


"  Chymia,  alias  Alchemia  et  Spagirica,  est  ars  corpora  vel  mixta,  vel  composita, 
vel  aggregata  etiam  in  principia  sua  resolvendi,  aut  ex  principiis  in  talia 
combinandi." — STAHL,  1723. 


NEW  YORK 
D.    APPLETON    AND    COMPANY 

1888 


V.  3,' 


PREFACE   TO   VOL.    III.,   PAKT   IV. 

THE  Fourth  Part  of  the  Treatise  on  Organic  Chemistry 
now  presented  to  the  public  includes  a  description  of  the 
Aromatic  Compounds  containing  seven  atoms  of  Carbon, 
and,  like  the  preceding  part,  forms  a  chapter  complete  in 
itself.  The  first  portion  is  concerned  with  the  Toluene 
Group,  then  come  the  Benzyl,  Benzoyl,  and  Hydrobenzyl 
Groups,  and  lastly  the  Xylene  Group  of  Eight  Carbon 
Compounds. 


CONTENTS. 


PAGE 

TOLUENE  GROUP 3 

Toluene  or  Methylbenzene 3 

Addition  Products  of  Toluene 6 

Chlorine  Substitution  Products  of  Toluene 7 

Monochlorotoluenes 8 

Dichlorotoluenes       .        ........       .       .       .        9 

Bromine  Substitution  Products  of  Toluene  .       .        .     •  .       .       .       .10 

Monobromotoluenes .       .       .        .10 

Dibromotoluenes 11 

Tribromotoluenes      .       . .12 

Tetrabromotoluenes  .        .        . 12 

Iodine  Substitution  Products  of  Toluene      .......      13 

Fluorine  Substitution  Products  of  Toluene 13 

Nitro-Substitution  Products  of  Toluene       .       .        .       .       .        .       .13 

Mononitrotoluenes 13 

Dinitrotoluenes 16 

Trinitrotoluenes         .       . .       .       .       .17 

Chloronitrotoluenes 19 

Bromonitrotoluenes  .        .        .       . 19 

Toluenesulphonic  Acids 20 

Toluenemonosulphonic  Acids          .       ....        .        .       .       .20 

Toluenedisulphonic  Acids       .       .       .       .       .        .       .       .       .        .22 

Toluenetrisulphonic  Acids .       .    -  22 

Monohydroxy toluenes  and  Allied  Bodies 23 

The  Cresols        . 23 

Dihydroxy  toluenes  and  Allied  Bodies 31 

Homocatechol  or  Homopyrocatechin 31 

Orcinol 37 

Substitution  Products  of  Orcinol 41 

Chlorine  Substitution  Products 41 

Bromine  Substitution  Products 41 

Iodine  Substitution  Products  .        . 41 

Nitro-Substitution  Products 41 

Cresorcinol 47 

Toluquinol  or  Toluhydroquinone 48 

Toluquinono 49 

Substitution  Products  of  Toluquinone 50 

Toluquinonoxime  Compounds        . 50 

Trihydroxytoluenes 53 


CONTENTS. 


PAGE 

TOLUENE  GROUP— continued. 

Amido-Derivatives  of  Toluene 54 

Amidotoluenes  or  Toluidines 54 

Halogen  Substitution  Products  of  the  Toluidines 67 

Chlorotoluidines 68 

Bromotoluidines 68 

lodotoluidines 68 

Nitrotoluidines 69 

Dinitrotoluidines 71 

Diamidotoluenes  or  Tolylenediamines           72 

Diazo-Derivatives  of  Toluene 74 

Hydrazine- Derivatives  of  Toluene 75 

Azo-Derivatives  of  Toluene 75 

Phosphorus  Derivatives  of  Toluene •        .        .83 

Arsenic  Derivatives  of  Toluene 84 

Antimony  Derivatives  of  Toluene 86 

Boron  and  Silicon  Derivatives  of  Toluene 87 

Mercury  Derivatives  of  Toluene 87 

BENZYL  GROUP 89 

Benzyl  Alcohol 89 

Benzyl  Ethers 94 

Ethereal  Salts  of  Benzyl 96 

Substitution  Products  of  Benzyl  Alcohol  and  its  Derivatives  ...  98 

Sulphur  Compounds  of  Benzyl 105 

Selenium  Compounds  of  Benzyl 109 

Nitrogen  Bases  of  Benzyl        . 110 

The  Benzylamines 110 

Amido-Substituted  Benzylamines 116 

Substitution  Products  of  the  Benzylamines 118 

Benzyl-Derivatives  of  the  Acid-Amides  and  Allied  Bodies        .        .        .  121 

Phosphorus  Compounds  of  Benzyl 124 

Arsenic  Compounds  of  Benzyl        .        .        .        .  • ]  25 

Silicon  Compounds  of  Benzyl 127 

BENZOYL  GROUP 128 

Benzaldehyde 129 

Benzidene  Compounds 136 

Substitution  Products  cf  Benzidene  Compounds 143 

Benzoic  Acid 151 

Salts  and  Ethers  of  Benzoic  Acid ]  60 

Oxides  of  Benzoyl 166 

Halogen  Compounds  of  Benzoyl 168 

Sulphur  Compounds  of  Benzoyl 170 

Nitrogen  Compounds  of  Benzoyl 172 

Hippuric  Acid 181 

Benzenyl  Compounds .194 

Benzonitril  and  its  Derivatives .197 

Benzimido- Ethers 200 

Benzenylamidines 202 

Benzenyloxime  Compounds 207 

Halogen-Substittition  Products  of  Benzoic  Acid 216 

Monochlorobenzoic  Acids 217 

Dichlorobenzoic  Acids 221 

Trichlorobenzoic  Acids     . 


CONTENTS.  ix 


BENZOYL  GROUP — continued. 

Tetrachlorobenzoic  Acid 222 

Monobromobenzoic  Acids 223 

Dibromobenzoie  Acids 224 

Tribromobenzoic  Acids 225 

Mono-Iodobenzoic  Acids 225 

Monofluorbenzoic  Acids 226 

Nitre-Substitution  Products  of  Benzoic  Acid 227 

Mononitrobenzoic  Acids 229 

Dinitrobenzoic  Acids ...  234 

Trinitrobenzoic  Acid 235 

Chloronitrobenzoic  Acids 236 

Bromonitrobenzoic  Acids 236 

lodonitrobenzoic  Acids 237 

Monamidobenzoic  Acids 237 

Chloramidobenzoic  Acids 254 

Bromamidobenzoic  Acids 255 

lodamidobenzoic  Acids 255 

Nitro-Amidobenzoic  Acids 255 

Dinitro-Amidobenzoic  Acids    .               257 

Piamidobenzoic  Acids 258 

Triamidobenzoic  Acid 260 

Diazo-Derivatives  of  Benzoic  Acid 260 

Hydrazinebenzoic  Acids 264 

Azo-Derivatives  of  Benzoic  Acid 265 

Monosulphobenzoic  Acids 268 

Disulphobenzoic  Acids 274 

Chlorosulphobenzoic  Acids 274 

Bromosulphobenzoic  Acids 274 

Mtrosulphobenzoic  Acids 275 

Amidosulphobenzoic  Acids 275 

Benzophosphinic  Acid 275 

Benzarsenic  Acids 277 

HYDROXYBENZYL  GROUP 279 

Hydroxybenzyl  Alcohols 279 

Hydroxybenzaldehydes 285 

Orthohydroxybenzaldebyde  or  Salicylaldehyde 285 

Substitution  Products  of  Salicylaldehyde 292 

Metahydroxybenzaldehyde 293 

Parahydroxybenzaldehyde 294 

Hydroxybenzoic  Acids 297 

Orthohydroxybenzoic  Acid  or  Salicylic  Acid 297 

Ethereal  Salts  of  Salicylic  Acid 306 

Salicylic  Ethers 306 

**    Ethereal  Salts  of  Salicylic  Ethers .        .  307 

Substitution  Products  of  Salicylic  Acid 313 

Metahydroxybenzoic  Acid 320 

Substitution  Products  of  Metahydroxybenzoic  Acid 323 

Parahydroxybenzoic  Acid 326 

Substitution  Products  of  Parahydroxybenzoic  Acid 334 

Substitution  Products  of  Anisic  Acid 336 

Anisenyloxime  Compounds 339 

Dibenzanishydroxylamine 341 


CONTENTS. 


PAGE 

HYDROXYBENZYL  GROUP — continued. 

Benzanisbenzhydroxylamine 341 

Anisdibenzhydroxylamine 341 

Anisbenzanishydroxylamine 342 

Dianisbenzhydroxylamine 342 

Benzdianishydroxylamine 342 

Dihydroxybenzyl  and  Dihydroxybenzoyl  Compounds    •    .  343 

Dihydroxybenzoic  Acids 350 

Protocatechuic  Acid  or  Orthodihydroxybenzoic  Acid         .        .       .        .350 

Symmetric  Metadihydroxybenzoic  Acid  or  o-Resorcylic  Acid  .       .        .  358 

Asymmetric  Metadihydroxybenzoic  Acid  or  j8-Resorcylic  Acid        .        .  359 

Adjacent  Metadihydroxybenzoic  Acid  or  7-Resorcylic  Acid      .        .        .  360 

Hydroxysalicylic  Acid  or  Paradihydroxybenzoic  Acid       ....  361 

Trihydroxybenzoic  Acids 363 

Gallic  Acid 363 

Pyrogallolcarboxylic  Acid 378 

Phloroglucinolcarboxylic  Acid 380 

Hydroxyquinolcarboxylic  Acid 380 

Constitution  of  the  Trihydroxybenzoic  Acids 381 

Quinic  Acid       .               381 

XYLENE  GROUP 386 

The  Xylenes  or  Dimethylbenzenes 390 

Substitution  Products  of  the  Xylenes 392 

Halogen  Substitution  Products  of  the  Xylenes 392 

Nitro-Substitution  Products  of  the  Xylenes 395 

Xylenesulphonic  Acids 398 

Hydroxy-Xylenes  or  Xylenols 399 

Dihydroxy-Xylenes 402 

Trihydroxy-Xylenes 403 

The  Xyloquinones 404 

Amido-Derivatives  of  the  Xylenes 405 

The  Amidoxylenes  or  Xylidines 405 

Nitroxylidines .  408 

Diamines  and  Triamines  of  the  Xylenes 409 

Xylyl-Compounds 410 

Xylyl  Alcohols r               .  411 

Xylylamines 412 

The  Tolualdehydes 413 

The  Toluic  Acids 414 

Hydroxytolualdehydes .  422 

Hydroxytoluic  Acids .               .  423 

Dihydroxytolualdehydes 427 

Dihydroxytoluic  Acids 428 

Xylylene  Alcohols     • 439 

Hydroxymcthylbenzoic  Acids 442 

Aldehydes  and  Aldehydo-Acids      .        .        .  447 

The  Phthalic  Acids '        \  .450 

Phthalic  Acid <  452 

Addition  Products  of  Phthalic  Acid     ...                                      .  469 

Halogen  Substitution  Products  of  Phthalic  Acid 471 

Nitrophthalic  Acids .  473 

Amidophthalic  Acids 475 

Sulphophthalic  Acids 476 


CONTENTS.  xi 


XYLENE  GROUP — continued. 

Isophthalic  Acid  or  Metaphthalic  Acid 479 

Addition  Products  of  Isophthalic  Acid 481 

Substitution  Products  of  Isophthalic  Acid 481 

Terephthalic  Acid 483 

Addition  Products  of  Terephthalic  Acid 486 

Substitution  Products  of  Terephthalic  Acid 488 

Hydroxymethylhydroxybenzoic  Acid 490 

Aldehydohydroxybenzoic  Acids 491 

Hydroxyphthalic  Acids 492 

Hydroxymethyldihydroxybenzoic  Acids 497 

Aldehydodihydroxybenzoic  Acids 502 

Dihydroxyphthalic  Acids        .        .        . 510 

Trihydroxyphthalic  Acids 519 

Tetrahydroxyphthalic  Acids 519 


ORGANIC    CHEMISTRY. 


ORGANIC    CHEMISTRY, 

OR    THE    CHEMISTRY    OF    THE    HYDROCARBONS    AND    THEIR 
DERIVATIVES. 


PART  IV. 
TOLUENE  GROUP. 

TOLUENE  OR  METHYLBENZENE,  C6H5.CH3. 

2017  This  hydrocarbon  was  discovered  by  Pelletier  and  Walter 
in  the  oil  obtained  as  a  by-product  in  the  manufacture  of  illu- 
minating gas  from  the  resin  of  Pinus  maritima.  They  named 
it  "  retinaphtha  "  (rdtinnaphte)  and  determined  its  composition 
accurately.1  Shortly  afterwards,  Couerbe  examined  the  liquid 
obtained  by  compressing  the  resin  gas,  and  isolated  from  it, 
among  other  hydrocarbons,  his  Heptacarbure  quadrihydrique, 
C7H±  ((7=6),  which,  in  spite  of  some  differences,  he  believed  to 
be  identical  with  retinaphtha.2  Deville  next  obtained  a  hydro- 
carbon of  the  same  composition  by  distilling  the  resin  contained 
in  Tolu  balsam.3  He  named  it  benzoene  (benzo&ne),  because,  in 
the  first  place,  the  balsam 4  from  which  it  had  been  obtained 
contains  benzoic  acid ;  secondly,  because,  according  to  his  for- 
mula, the  hydrocarbon  may  be  looked  upon  as  the  type  of  the 

1  Ann.  Chim.  Phys.  Ixvii.  269  ;  Pogg.  Ann.  xliv.  8. 

2  Ann.  Chim.  Phys.  Ixix.  184  ;  Journ.  Prakt.  Chem.  xviii.  165. 

3  Ann.  Chim.  Phys.  [3]  iii.  168  ;  Journ.  PraJct.  Chem.  xxv.  336. 

4  Tolubalsam   is   obtained  by  incisions  made   in  the  bark  of  the  Myroxylon 
toluifcra,  as  mentioned  by  the  Spanish  physician  Monardes  in  his  Historia  de  las 
cosas  que  se  traen  de  nucstras  Indias  occidentals,  which  first  appeared  complete 
in  Seville  in  1574,  and  in  which  he  says  that  the  balsam  was  collected  by  the 
Indians,  in  the  district  Tolu,  in  the  neighbourhood  of  Carthagena  (Fliickiger  and 
Hanbury,  Phar?nacographia). 


AROMATIC  COMPOUNDS. 


benzole  series,  and  finally,  because  this  name  was  similar  to  that 
of  benzine  (benzene),  to  which  the  substance  bears  the  greatest 
resemblance.  He  considered,  nevertheless,  that  benzoene,  was 
not  identical,  but  isomeric  with  retinaphtha;  Glenard  and 
Boudault  also  considered  the  dracyl,  which  they  had  obtained, 
by  the  dry  distillation  of  dragon's  blood  (from  Calamus  draco),1 
to  be  an  isomeride  of  the  former. 

Hofmann  and  Muspratt  then  showed  that  it  is  identical  with 
benzoene,  for  which  somewhat  unsuitable  name  Berzelius  sub- 
stituted that  of  toluol,2-  soon  universally  accepted,  and  still  in 
use  on  the  Continent,  while  in  England  it  has  been  changed 
for  the  sake  of  consistency  into  toluene. 

A  complete  investigation  of  toluene  has  proved  that  not  only 
as  regards  its  empirical  formula,  but  in  all  its  properties,  it  is 
the  next  higher  homologue  of  benzene.  Deville,  as  well  as 
Gldnard  and  Boudault,  had  already  obtained  from  it  nitrotoluene, 
C7H7NO2  (nitrobenzoene,  nitrodracyl),  by  the  action  of  nitric 
acid,  and  Hofmann  and  Muspratt  converted  this  by  reduction 
into  toluidine,  C7H7NH2,  which  resembles  aniline  very  closely.3 

Noad  found  that  when  cymene,  C10H14,  which  is  a  constituent 
of  Roman  cumin-oil,  is  oxidized  with  nitric  acid,  toluic  acid, 
C8H802,  the  homologue  of  benzoic  acid,  is  formed,  and  on  dis- 
tillation with  caustic  baryta  decomposes  into  carbon  dioxide  and 
toluene,  a  reaction  which  corresponds  exactly  to  the  formation  of 
benzene  from  benzoic  acid.4 

The  relation  of  toluene  to  the  benzoic  series,  which  had 
already  been  pointed  out  by  the  French  chemists,  was  experi- 
mentally proved  by  Cannizzaro,  who  found  that  benzyl  alcohol, 
C7H7O,  which  is  converted  by  oxidation  into  benzoic  acid,  under- 
goes a  simultaneous  oxidation  and  reduction  when  heated  with 
concentrated  alcoholic  potash,  benzoic  acid  and  toluene  being 
formed.5 

Finally,  Fittig  and  Tollens  ascertained  the  constitution  of 
toluene.  These  chemists  obtained  it  synthetically  by  the  action 
of  sodium  on  a  mixture  of  methyl  iodide  and  bromobenzene,6  by 
which  reaction  they  not  only  proved  that  the  product  is  methyl- 
benzene,  but  pointed  out  a  general  and  simple  method  by  which 
the  higher  homologues  can  be  prepared,  and  their  constitutions 
determined. 

1  Journ  Prakt.  Chem.  xxxi.  Ill  ;  xxxiii.  466.  2  Jahrcsb.  xxii.  354. 

3  Chem.  Soc.  Mem.  (1845)  ii.  367.  4  jbid.  iii.  421. 

5  Ann.  Chem.  Fharm.  xc.  252.  «  Ibid,  cxxxi.  303. 


TOLUENE. 


Mansfield,  whose  results  were  subsequently  confirmed  by 
Ritthausen,  was  the  first  to  prove  that  light  coal-tar  oils  contain 
toluene  and  higher  homologues  as  well  as  benzene1  (Part  III. 
p.  66).  Toluene  also  occurs,  together  with  xylene,  in  wood-tar  ; 
Cahours  detected  it  in  crude  French  pyroligneous  acid,2  and  Volkel 
in  the  oil  which  comes  over  first  in  the  distillation  of  beech-wood 
tar.3  It  is  also  found,  together  with  its  homologues,  in  several 
varieties  of  petroleum,  such  as  that  from  Burmah  (Rangoon  tar),4 
as  well  as  in  the  liquid  obtained  by  the  compression  of  the 
illuminating  gas  which  is  manufactured  by  heating  the  high 
boiling  portions  of  petroleum,  and  has  been  used  for  lighting 
railway  carriages.5  It  is  obtained  on  the  large  scale  from  light 
coal-tar  oil,  and  is  chiefly  employed  in  the  colour  industry. 

Properties.  —  .Toluene  is  a  strongly  refractive  liquid,  possessing 
a  smell  similar  to  that  of  benzene;  it  boils  at  11  0*3°  and  does 
not  solidify  at  —20°.  Oxidizing  agents  convert  it  into  benzoic 
acid.  It  combines  with  aluminium  chloride  forming  the  com- 
pound Al2Cl6+6  C7H8,  a  thickish,  orange-coloured  liquid,  which 
is  violently  decomposed  by  water  with  separation  of  toluene. 
A  similar  compound  is  formed  with  aluminium  bromide.6 

When  toluene  is  heated  with  aluminium  chloride  to  200°,  a 
portion  of  it  is  converted  into  paradimethylbenzene,  paramethyl- 
ethylbenzene,  and  metamethylethylbenzene,  high  boiling  hydro- 
carbons being  also  formed,  while  benzene  under  the  same  con- 
ditions yields  toluene,  ethylbenzene  and  diphenyl. 

In  order  to  explain  this  remarkable  reaction,  Friedel  and 
Crafts  7  assume  that  the  following  first  takes  place  : 


2C6H5A12C16  +  2HC1  =  C12H10+  2A12C16+  2H2. 

The  nascent  hydrogen  and  the  hydrochloric  acid  convert  a. 
portion  of  the  benzene  into  methyl  chloride  and  ethyl  chloride,, 
which  then  form  toluene  and  ethyl  benzene  (Pt.  III.  p.  14.)  : 

C6H5.  A12C15  +  CH3C1  =  C6H6.CH3  +  A12C16. 

When  toluene  is  employed,  a  similar  reaction  takes  place  ;- 
methyl  chloride  is,  however,  probably  formed  simultaneously, 
according  to  the  equation  : 

C6H5.CH3  +  A12C16  =  C6H5  A12C16  +  CH3C1. 

1  Journ.  PraU.  Chem.  Ixi.  74.  2  Ann.  Chem.  Pharm.  Ixxvi.  286. 

3  Ibid.  Ixxxvi.  335.  4  Journ.  Prakt.  Chem.  Ixx.  300. 

8  Greville  Williams,  Chem.  News,  xlix.  197. 
6  Guatavson,  Ber.  Deutsch.  Chem.  Ges.  xi.  2152.  7  Compt.  rend.  c.  692.. 

232 


AROMATIC  COMPOUNDS. 


When  one  part  of  chromium  oxychloride  is  dissolved  in  ten 
parts  of  carbon  disulphide,  and  the  solution  allowed  to  drop  into 
a  mixture  of  one  part  of  toluene  and  ten  parts  of  carbon'  disul- 
phide, a  chocolate-brown,  crystalline  precipitate  of  the  empirical 
formula  C7H8+2OO2C12  is  formed;  this  is  soluble  in  glacial 
acetic  acid,  rapidly  absorbs  moisture,  and  is  decomposed  by 
water  with  formation  of  benzaldehyde  and  chromous  chromate, 
showing  that  it  is  benzidenedichlorochromic  acid  :  • 


OCrCl2.OH 
\OCrCl.OH 


CflH5.CH<  +  H20  =  C6H5.CHO  +  4HC1  +  2CrO2. 


Alcohol  and  ether  exert  a  similar  action,  ethyl  chloride  being 
formed  in  these  cases.  On  heating  the  compound  to  240°—  245°, 
the  chloride,  C6H5.CH  (OOOC1)2,  is  obtained  ;  it  has  a  darker 
colour  and  is  more  stable  in  moist  air,  but  behaves  towards 
water  similarly  to  the  acid.1 


ADDITION  PRODUCTS  OF  TOLUENE. 

2018  Dihydrotoluene,  C7H10,  is  obtained  by  heating  toluene 
with  phosphonium  iodide  to  350°,  and  is  a  liquid  boiling  at 
105°-108°.2 

Tetrahydrotoluene,  C7H12,  occurs  in  the  distillation  products  of 
pine  resin  and  colophonium,  which  are  obtained  on  the  large 
scale,  and  employed  in  the  manufacture  of  varnishes,  &c.  The 
fraction  boiling  below  300°,  which  forms  the  smaller  portion  and 
is  known  as  "  resin  spirit "  or  "  essence  of  resin,"  is  a  mixture  of 
fatty  acids,  aldehydes,  paraffins,  olefmes,  aromatic  hydrocarbons  and 
their  addition  products,3  among  which  is  tetrahydrotoluene.  This 
substance  is  a  liquid  boiling  at  103°— 105°,  and  is  converted  by 
bromine  into  a  crystalline  bromide,  C7H6Br6.  Tetrahydrotoluene 
combines  with  water  to  form  a  hydrate,  C7H12-J-2H2O,  which 
crystallizes  in  long,  white  crystals,  and,  according  to  Renard,  is 
identical  with  Anderson's  colophonin,  C7H14O2,  obtained  by 
exposing  resin  spirit  to  the  air  for  a  long  period  ; 4  while  accord- 

1  fitard,  Ann.  Chim.  Phys.  [5]  xxii.  223. 
-   IJaoyer,  Ann.  Chem.  Pfiarm.  civ.  271. 

3  Kelbe,  ibid.  ccx.  10  ;  Kelbe  and  Bauer,  Ber.  Deutsch.   Chem.  Ges.  xvi.  2559  ; 
Renard,  Ann.  Chim.  Phys.  [6],  i.  223. 

4  Chem.  News,  xx.  76. 


TOLUENE  SUBSTITUTION  PRODUCTS. 


ing  to  Tichborne,  colophonin  hydrate,  C10H22O3  -f  H2O,  is  formed, 
and  loses  water  on  heating.1 

Hexhydrotoluene,  C7H14,  is  prepared  by  heating  toluene  with 
a  large  excess  of  concentrated  hydriodic  acid  to  2800,2  and 
occurs  in  Baku  petroleum 3  and  in  resin  spirit  (Renard).  It 
is  a  liquid  smelling  like  petroleum,  boiling  at  97°,  and  having 
a  specific  gravity  of  772  at  0°.  A  mixture  of  concentrated 
sulphuric  and  nitric  acids  does  not  attack  it  in  the  cold,  but 
when  hot  oxidizes  it  completely. 


CHLORINE    SUBSTITUTION    PRODUCTS 
OF   TOLUENE. 

2019  By  the  action  of  chlorine  on  toluene  in  the  dark,  Deville 
obtained  Benzo&ne  monochlord,  C7H7C1,  as  a  thin  liquid  boiling  at 
1700,4  whilst  Cannizzaro  found  that  the  monochlorinated  toluene 
obtained  by  the  repeated  distillation  of  toluene  in  a  stream  of 
chlorine,  and  boiling  at  175°,  is  identical  with  benzyl  chloride, 
as  it  can  be  readily  converted  into  benzyl  alcohol.5  The  same 
compound  was  also  obtained  by  passing  chlorine  into  toluene, 
but  in  this  process  an  isomeric  compound  was  frequently  formed 
instead  of  the  benzyl  chloride,  and  this  proved  to  be  as  stable 
as  chlorobenzene.  These  enigmatical  results  were  explained  by 
Beil  stein  and  Geitner,6  who  observed  that  the  action  of  chlorine 
on  toluene  varies  according  to  the  temperature  at  which  the 
chlorination  is  effected.  Benzyl  chloride  alone  is  formed  when 
the  mixture  is  hot,  while  the  stable  chlorotoluene  is  formed 
when  the  process  is  conducted  in  the  cold.  As,  however,  heat  is 
evolved  by  the  action  of  the  chlorine,  the  toluene,  if  used  in 
large  quantities  and  not  carefully  cooled,  may  become  heated 
almost  to  the  boiling  point,  benzyl  chloride  consequently  being 
formed  together  with  more  or  less  chlorotoluene.  The  nature  of 
this  mixture  can  readily  be  exhibited  by  oxidizing  it  with 
chromic  acid,  the  benzyl  chloride  being  thus  converted  into 
benzoic  acid,  and  the  chlorotoluene  into  chlorodracylic  acid 

1  Chem.  News,  xx.  38. 

2  Wreden  and  Znatowicz,  Ann.  Chem.  Pharm.  clxxxvii.  161. 

3  Beilstein  and  Kurbatow,  ibid.  xiii.  1818  ;  see  also  xiv.  1620. 

4  Ann.  Chim.  Phijs.  [3],  iii.  178. 

5  Ann.  Chem.  Pharm.  xcvi.  246  ;  ibid.  cxli.  198. 

6  Ibid,  cxxxix.  331. 


AROMATIC  COMPOUNDS. 


(parachlorobenzoic  acid),  the  acids  being  readily  separated  by 
means  of  the  very  great  difference  in  their  solubilities  in  water. 

Beilstein  and  Geitner  further  found  that  chlorotoluene  is  more 
readily  obtained  by  dissolving  a  little  iodine  in  the  toluene  and 
then  chlorinating,  under  which  conditions  no  benzyl  chloride  is 
formed  either  in  the  cold  or  on  heating. 

As  already  mentioned  (Part  III.  p.  17)  all  the  hydrogen  atoms 
of  the  aromatic  group  can  be  thus  replaced  by  chlorine,  whilst  at 
the  boiling  point,  in  absence  of  iodine,  substitution  can  only  take 
place  in  the  methyl  group.  By  working  alternately  according  to 
these  two  methods  no  octochlorotoluene  can  be  obtained,  the 
final  products  being  pentachlorobenzidene  chloride,  C6C16.OHC12 
and  tetrachlorobenzal  chloride,  C6HC14.CC13.  If  these  be  heated 
with  antimony  pentachloride  in  order  to  effect  a  further  chlorina- 
tion,  they  decompose  with  formation  of  hexchlorobenzene.1 


MONOCHLOROTOLUENES,  C6H4C1.CH3. 

2020  Orthochlorotoluene  is  formed  only  in  small  quantities  by 
the  chlorination  of  toluene  in ,  the  presence  of  iodine  :  it  may, 
however,  be  readily  obtained  from  orthotoluidine  by  means  of 
the  diazo-reaction.2  It  is  a  liquid  boiling  at  157°,  which  is 
oxidized  by  potassium  permanganate  to  orthochlorobenzoic  acid, 
whilst  chromic  acid  solution  produces  complete  oxidation.3 

Mctachlorotoluene  is  not  formed  by  the  action  of  chlorine  on 
toluene ;  it  has  been  prepared  from  metatoluidine,  as  well  as 
from  paratoluidine  by  converting  this  into  acetoluide,  C6H4(CH3) 
NH(C2H30),  chlorinating  and  decomposing  the  product  by  heat- 
ing with  caustic  potash ;  the  monochloroparatoluidine  thus  ob- 
tained is  converted  into  the  diazo-compound,  and  then  decom- 
posed with  absolute  alcohol ; 4  chloroparatoluidine  has,  therefore, 
the  following  constitution  •. 

CH3 


01 
NH2. 

1  Beilstein  and  Kuhlberg,  Ann.  Chem.  Pharm.  cl.  286. 

2  Ibid.  clvi.  79  ;   Gascorowski  and  Wayss,  Ber.  Deutsch.   Chem.  Ges.  xviii. 

8  Emraerling,  Ber.  Deutsch.  Chem.  Ges.  viii.  880. 
4  Wroblevsky,  Ann.  Chem.  Pharm.  clxviii.  199. 


CHLOROTOLUENES. 


Hence  we  see  that,  on  the  chlorination  of  paratoluidine,  the 
chlorine  takes  up  the  position  adjacent  to  the  basic  group,  and 
this  also  occurs  in  many  other  cases. 

Metachlorotoluene  is  a  liquid  which  boils  at  15(T  and  is  con- 
verted by  oxidation  into  metachlorobenzoic  acid. 

Parachlorotoluene  is  the  chief  product  of  the  action  of  chlorine 
on  toluene  in  the  presence  of  iodine.1  It  is  advantageous  to 
substitute  molybdenum  pentachloride  for  iodine,  and  to  pass  the 
chlorine  through  the  mixture  heated  on  the  water-bath.2  The 
product  thus  obtained  does  not  solidify  when  cooled  to  a  low 
temperature,  since  it  contains  various  substances,  such  as  the 
•ortho-compound,  &c.,  as  impurities.  If  the  parachlorotoluene 
be  prepared  from  paratoluidine,  it  is  obtained  in  a  pure  condi- 
tion, and  then  boils  at  160'5°  and  solidifies  at  0°  to  a  foliaceous 
mass,  melting  at  6'5°.3  On  oxidation  it  is  converted  into  para- 
chlorobenzoic  acid. 


DlCHLOROTOLUENES,    C6H3C12.CH3. 

2021  When  toluene  is  treated  with  sufficient  chlorine  in 
presence  of  iodine  or  molybdenum  pentachloride,  and  the  pro- 
duct purified  by  fractional  distillation,  a  liquid  boiling  at  196°  is 
obtained,4  which,  in  spite  of  its  constant  boiling  point,  is  not  a 
definite  compound,  but  a  mixture  of  three  dichlorotoluenes.  If 
chlorine  be  passed  into  the  vapour  of  the  boiling  liquid  until  no 
further  action  takes  place,  the  hydrogen  of  the  methyl  group  is 
replaced  by  chlorine  and  the  corresponding  dichlorobenzenyl- 
trichlorides  formed  ;  on  heating  with  water  to  200°  these  are 
converted  into  three  dichlorobenzoic  acids : 

C6H3C12.CC13  +  2H20  =  C6H3C12.C02H  +  3HC1. 

The  formation  of  three  dichlorotoluenes  can  readily  be  explained  ; 
the  monochlorotoluene,  which  is  first  formed,  consists  chiefly  of 
the  para-compound,  which  can  yield  two  isomeric  dichloro- 
toluenes, whilst  the  third  is  formed  from  the  orthochlorotoluene 
which  is  also  present,  though  in  smaller  quantity. 

The     mixture     appears    to    consist    chiefly    of    asymmetric 

1  Beilstein  and  Geitner,  loc.  tit. 

2  Aronheim  and  Dietrich,  Ber.  Deutsch.  Chcm.  Gcs.  viii.  1402. 

3  Hiibner  and  Majert,  ibid.  vi.  794. 

4  Beilstein  and  Geitner  ;  Beilstein  and  Euhlberg,  Ann.  Chem.  Pharm.  el.  313  ; 
Sclmltz,  ibid,  clxxxvii.  263.     Aronheim  and  Dietrich. 


10  AROMATIC  COMPOUNDS. 

dichlorotoluene,  (CH3  :C1  :C1  — 1  :3  :  4),  which  yields  the  cor- 
responding dichlorobenzoic  acid  on  oxidation. 

Dichlorotoluene  hexchloride,  C6H3C12(CH3)C16,  is  obtained  by 
the  continued  action  of  chlorine  on  toluene  in  the  cold,  and 
crystallizes  from  carbon  disulphide  in  large  prisms  melting  at 
150°.  When  it  is  heated  with  alcoholic  potash  to  110°,  tetra- 
chlorotoluene,  C6HC14.CH3,  is  formed ;  this  compound  is  a  liquid 
boiling  at  280°-290°.1 

The  following  substitution  products  have  been  obtained  by 
the  continued  action  of  chlorine,  assisted  finally  by  the  addition 
of  antimony  chloride  : 

Melting-  Boiling- 

point,  point. 

a-Trichlorotoluene2    C6H2C13.CH3(2  :  4  :  5)     82°  230° 

/9-Trichlorotoluene3    C6H2C13.CH3(2  :  3  :  4)     41°  232° 

Tetrachlorotoluene4    C6HC14.CH3  96°  276°'5 


Pentachlorotoluene  5    C6C15.CH3  218°  301' 


BROMINE    SUBSTITUTION    PRODUCTS    OF 
TOLUENE. 

2022  All  the  theoretically  possible  compounds  of  this  series 
are  known. 

MONOBROMOTOLUENES,  C6H4Br.CH3. 

Ortholromotoluene  is  formed,  together  with  a  larger  amount  of 
parabromotoluene,  by  the  bromination  of  toluene  in  the  cold. 
The  para-compound,  which  crystallizes  out,  is  removed  by 
pressing,  and  the  liquid  cooled  in  a  freezing  mixture,  in  order  to 
remove  as  much  of  the  solid  as  possible  ;  the  portion  which 
remains  liquid  is  then  dissolved  in  alcohol  and  distilled,  all  the 
remaining  parabromotoluene  volatilizing  in  the  vapour.6  The 
para-compound  may  also  be  removed  by  means  of  sodium,  which 
does  not  act  upon  the  ortho-compound  in  the  cold.7  In  order 
to  effect  this,  the  liquid  is  dissolved  in  benzene  and  allowed  to 
stand  over  sodium  for  eight  days ;  it  is  then  distilled,  and  the 
fraction  boiling  between  170° — 190°  treated  three  or  four  times 
in  the  same  way.8 

1  Pieper,  Ann.  C'hcm.  Pharm.  cxlii.  304. 

2  Lirnpricht,   ibid,   cxxxix.   326  ;    Schultz  ;  Aronheim  and   Dietrich  ;    Seelig, 
Ber.  Dcutsch.  Chem.  Ges.  xviii.  420. 

3  Seelig.  4  Limpricht ;  Beilstein  and  Kuhlberg. 
8  Beilstein  and  Kuhlberg. 

6  Hiibner  and  Jannasch,  Ann.  Chem.  Pharm.  clxx.  117. 

7  Luginin,  Bull.  Soc.  Chim.  iv.  514.  8  Reymann,  ibid.  xxvi.   533. 


BROMOTOLUENES.  11 


Orthobromotoluene  has  also  been  prepared  from  ortho- 
toluidine  by  means  of  the  diazo-reaction.1  It  is  a  liquid,  boiling 
at  182° — 183°  and  is  oxidized  by  dilute  nitric  acid  to  orthobromo- 
benzoic  acid,  while  chromic  acid  causes  complete  combustion. 

Mctabromotoluene  has  been  obtained  from  metatoluidine  and 
from  parabromotoluidine  (Wroblevsky).2  It  is  a  liquid  which 
boils  at  184-3°  (Korner)  and  does  not  solidify  at  -  20°. 

Parabromotoluene.  The  separation  of  this  from  orthobromo- 
toluene  is  described  above.  It  may  be  more  rapidly  effected  by 
agitating  the  rectified  mixture  with  half  its  volume  of  fuming 
sulphuric  acid ;  the  parabromotoluene  separates  out  as  a 
crystalline  mass  after  some  time.3  It  boils  at  182'5°,4  and  is 
deposited  from  an  alcoholic  solution  in  rhombic  crystals  melting 
at  28 '5°.  When  given  to  a  dog,  it  appears  in  the  urine  as 
parabromohippuric  acid  and  parabromobenzoic  acid.  When  it  is 
treated  with  chromium  oxychloride,  bromobenzidenedichloro- 
chromyl  chloride,  C6H4Br.CH(OCrOCl)2  is  formed  as  a  brown 
precipitate  which  is  decomposed  by  water  with  formation  of 
parabromobenzaldehyde  (6tard). 


DlBROMOTOLUENES,  C6H3Br2.CH3. 

2023  These  have  been  prepared  from  the  monobromotoluidines 
by  the  replacement  of  the  amido-group  by  bromine,  and  from 
the  dibromotoluidines  by  the  replacement  of  the  amido-group 
by  hydrogen.5  The  first  compound  in  the  following  list  has  also 
been  obtained  by  the  direct  bromination  of  toluene  ;  the  process 
goes  on  much  more  rapidly  in  the  presence  of  iodine  and  in  the 
sunlight.6 

Melting-  Boiling- 

CH3  :  Br  :  Br  point.  point. 

134  liquid,  does  not  solidify  at -20°  240° 
126         „             „             „              „  246° 
125,,             „             „              „  236° 
1^4,,              „              „               „ 

123     solid 28° 

135  long  needles     ......  39°  246° 

1  Wroblevsky,  Ann.  Chem.  Pharm.  clxviii.  171. 

2  See  also  Grete,  ibid,  clxxvii.  231. 

3  Hiibner  and  Wallaeh,  Ann.  Chem.  Pharm.  cliv.  293. 

4  Hiibner  and  Post,  ibid,  clxix.  6. 

5  Wroblevsky,  ibid,  clxviii.   161  ;  Neville  and  Winther,   Bcr.  Deutsch.  Chem. 
Ges.  xiii.  962  ;  xiv.  417. 

6  Jannasch,  Ann.  Chem.  Pharm.  clxxvi.  286. 


12  AROMATIC  COMPOUNDS. 

On  treatment  with  nitric  acid  they  yield  all  the  mononitro- 
compounds  which  are  theoretically  possible  ;  most  of  these  com- 
pounds crystallize  in  needles. 


TRIBROMOTOLUENES,  C6H2Br3.CH3 

These   are   obtained   in  a  similar  manner   to   the  preceding 

compounds.1 

Melting-  Boiling- 

CH3  :  Br  :  Br  :  Br  :  point.  point. 

1345  crystals  ....  88°— 89° 

1234  crystals  ....  46° 
1246  long  needles  .    .  66°                   290° 

1235  flat  needles    .    .  52°'5 
1245  long  needles  .    .  112° 
1256  flat  needles    ,  58°— 59°              — 


TETRABROMOTOLUENES,  CGHBr4.CH3.2 

Melting-  Boiling- 

CH3  :  Br  :  Br  :  Br  :  Br  :  point.  point. 

12345  thin  needles  .        Ill0— 1110'5 
12356         fine  needles    .        116°— 117° 

12346  crystals  .    .    .        105°— 108° 

Pentabromotohiene,  C6Br5.CH3,  is  formed  when  toluene  is 
allowed  to  drop  into  bromine  which  is  free  from  chlorine  and  to 
which  some  aluminium  bromide  has  been  added,  as  well  as  by 
replacing  the  amido-group  of  tetrabromotoluidine  by  bromine 
(Neville  and  Winther).  It  crystallizes  from  benzene  in  long 
needles,  melting  at  282°— 283°. 

When  toluene  is  treated  with  an  excess  of  bromine  containing 
iodine,  and  the  temperature  finally  allowed  to  rise  to  350° — 400°, 
hexbromobenzene  and  tetrabromomethane  are  formed,  the  latter 
being,  however,  for  the  most  part  converted  into  the  former.3 

1  Wroblevsky  ;  Neville  and  Winther,  loc.  cit. 

2  Ibid.  3  Gessner,  JSer.  Deutsch.  Chem.  Gcs.  ix.  1508. 


NITROTOLUENES.  13 


IODINE    SUBSTITUTION    PRODUCTS    OF 
TOLUENE. 

Only  the  mono-iodotoluenes,  C6H4LCH3,  which  are  obtained 

from  the  toluidines,  are  known.1 

Boiling-  Melting- 

point,  point. 

Ortho-iodotoluene         liquid  .    .  204° 

Meta-iodotoluene  „      .    .  204° 

Para-iodotoluene  plates  .    .  211°'5  35° 


FLUORINE   SUBSTITUTION   PRODUCTS   OF 
TOLUENE. 

Fluotoluene,  C6H4F.CH3,  is  formed  when  the  diazo-compound 
obtained  from  paramidotoluenesulphonic  acid  is  decomposed 
with  strong  hydrofluoric  acid.  It  is  a  liquid  smelling  of  bitter 
almonds,  and  boiling  at  1140.2 


NITRO-SUBSTITUTION   PRODUCTS   OF 
TOLUENE. 

MONONITKOTOLUENES,  C(.H4(N0.2)CH3. 

2024  By  dissolving  toluene  in  fuming  nitric  acid  and  pre- 
cipitating with  water,  Deville  obtained  nitrotoluene  (protonitro- 
benzo&ne)  as  a  colourless  liquid  boiling  at  225°,  and  possessing  a 
smell  of  bitter  almonds  and  a  very  sweet,  somewhat  biting  taste. 
This  compound  was  then  repeatedly  prepared  by  many  chemists, 
who  confirmed  Deville's  statements. 

These  circumstances  served  to  render  the  following  observations 
of  Jaworsky  the  more  remarkable ;  this  chemist  found  that 
when  nitrotoluene  is  dissolved  in  fuming  nitric  acid,  and  water 
added  to  the  solution,  a  precipitate  is  formed  which  separates 
from  a  hot,  alcoholic  solution  in  lustrous  crystals  melting  at  54° 

1  Beilstein  and   Kuhlberg,  Ann.  Cliem.   Pharm.  clviii.  147  ;  Korner,  Zeitschr. 
Chcm.  clxxxviii.  327. 

2  Paterae  and  Oliveri,  Gaz.  Chim.  Ital.  xiii.  533. 


14  AROMATIC  COMPOUNDS. 

and  which,  boiling  without  decomposition  at  238°,  has  exactly 
the  same  composition  as  nitrotoluene.  He  obtained  the  same 
compound  by  continuing  the  distillation  of  the  liquid  nitrotoluene 
to  240° ;  the  residue,  which  solidified  on  cooling,  was  identical 
with  the  product  obtained  by  the  other  method.  He  concluded 
from  these  experiments  that  pure  nitrotoluene  is  a  solid  body, 
the  crystallizing  power  of  which  is  usually  destroyed  by  liquid 
impurities,  these  also  having  the  power  of  lowering  the  boiling 
point.1 

These  observations  were  confirmed  by  other  chemists  and 
were  even  taken  advantage  of  commercially,  for  well  crystallized 
nitrotoluene  was  manufactured  on  the  large  scale  in  Paris  in 
1867.  Alexejew  confirmed  Jaworsky's  view  by  obtaining  the  same 
azotoluene  from  the  solid  as  from  the  liquid  nitrotoluene.2  He 
also  found  that  the  solid  compound  is  converted  by  reduction 
into  a  solid  toluidine,3  which  could  not  be  obtained  from  the 
liquid  compound. 

Kekule,  who  also  investigated  these  facts,  confirmed  the 
above  observation,  and  showed  in  addition  that  the  solid  nitro- 
toluene is  more  readily  oxidized  to  paranitrobenzoic  acid  and 
gives  a  better  yield  than  the  liquid ;  the  lower  boiling  portion 
of  the  latter  yielded  a  liquid  toluidine  containing  aniline,  and 
he  therefore  considered  it  probable  that  the  substance  which 
had  up  to  that  time  been  looked  upon  as  nitrotoluene  was  a 
mixture  of  nitrobenzene  and  nitrotoluene.4 

Rosenstiehl,  however,  made  the  discovery  that  the  ordinary 
liquid  toluidine  is  a  mixture  of  the  solid  with  the  isomeric  pseudo- 
toluidine,5  and  that,  consequently,  two  nitrotoluenes  are  formed  by 
the  nitration  of  toluene.6  In  order  to  decide  the  question 
whether  toluene  itself  is  a  mixture  of  two  isomeric  hydrocarbons, 
he  investigated  the  behaviour  of  samples  of  toluene  from  various 
sources  towards  nitric  acid.  He  took  some  which  had  been 
previously  exposed  to  a  red  heat,  and  some  which  he  had 
obtained  by  the  decomposition  of  xylene,  C6H4(CH3)2,  at  a  high 
temperature.  He  also  investigated  toluene  synthetically 
prepared,  and  that  obtained  from  Tolu  balsam.  In  all  cases  he 
obtained  the  two  toluidines.  Finally,  Berthelot  reduced  these 
by  heating  with  hydriodic  acid  and  obtained  one  and  the  same 
toluene.7 

1  Zcitschr.  Ckem.  1865,  222.  2  Ibid.  1866,  269. 

3  Bull  SM.  Chim.  vii.  376.  4  Zcitschr.  Chem.  1867,  225. 

5  Ibid.  1868,  557.  6  Ibid.  1869,  190. 

7  Ibid. 


XITROTOLUENES.  15 


Hence  the  supposition  appeared  not  improbable  that  the  lower 
boiling  portion  of  ordinary  nitrotoluene  would  be  an  isomeride 
of  the  solid  compound,  which  yields  the  pseudotoluidine ; 
Rosenstiehl,  however,  singularly  enough,  did  not  investigate  this 
point,  and  it  was  reserved  for  Beilstein  and  Kuhlberg  to  answer 
the  question.  These  chemists  had  already  prepared  the 
liquid  /3-nitrotoluene  from  dinitrotoluene,  by  converting  the 
latter  into  nitrotoluidine,  C6H3(NH2)(N02).CH3,  by  partial 
reduction  with  ammonium  sulphide,  and  then  replacing  the 
amido-group  by  hydrogen.  They  then  found  that  this  nitro- 
toluene, which  they  called  metanitrotoluene,  but  which  is  now 
known  as  the  ortho-compound,  forms  the  more  volatile  portion  of 
crude  nitrotoluene  and  can  be  separated  from  the  solid  paranitro- 
toluene  by  repeated  careful  fractional  distillation.1 

A  small  quantity  of  metanitrotoluene  is  formed,  together  with 
the  ortho-  and  para-compounds,  by  the  action  of  fuming  nitric 
acid  on  toluene.2  The  relative  quantities  of  the  two  chief  pro- 
ducts which  are  formed  depend  upon  the  concentration  of  the 
acid,  and  the  temperature  at  which  the  nitration  is  effected. 
When  a  very  concentrated  acid  is  employed  and  the  temperature 
allowed  to  rise,  paranitrotoluene  is  chiefly  obtained,  while  the 
yield  of  the  ortho-compound  is  greatly  increased  by  employing  a 
weaker  acid  and  cooling  the  mixture  well. 

The  nitrotoluenes  are  manufactured  on  the  large  scale,  by 
mixing  10  parts  of  toluene  with  11  parts  of  nitric  acid  of 
specific  gravity  1*22  and  1  part  of  sulphuric  acid  of  specific 
gravity  1*33  with  continual  agitation,  in  the  apparatus  used 
for  the  manufacture  of  nitrobenzene ;  the  mixture  is  then 
either  cooled  or  kept  warm  according  to  the  product  desired. 
The  crude  product  is  washed  with  water  and  caustic  soda 
solution,  freed  from  unattacked  toluene  by  distillation  with 
steam,  and  then  distilled  with  super-heated  steam.  The 
distillate  is  then  repeatedly  fractionated ;  the  larger  portion  of 
the  fraction  distilling  above  230°  solidifies  on  cooling,  and  the 
crystals,  after  purification  by  draining  and  pressing,  yield  pure 
paranitrotoluene  on  distillation;  the  fraction  boiling  between 
222° — 223°  consists  chiefly  of  orthonitrotoluene,  while  the  inter- 
mediate fractions  contain  some  of  the  meta-compound. 

Ortlionitrotoluene  is  obtained  pure  when  the  amido-group  of 
the  isomeric  nitrotoluidines,  which  contain  the  nitroxyl  in  the 

1  Ann.  Chem.  Pharni.  civ.  i. 

2  Monnet,  Reverdin  and  Nolting,  Ber.  Deutsch.  Chem.  Gcs.  xii.  445. 


16  AROMATIC  COMPOUNDS. 

ortho-relation  to  the  methyl  group,  is  replaced  by  hydrogen: 
this  is  best  effected  by  heating  the  compound  with  alcohol 
saturated  with  nitrogen  trioxide.  It  is  a  liquid  which  boils  at 
223°,  does  not  solidify  at  —  20°,  and  has  a  specific  gravity  of  T163 
at  23-5°. 

Metanitrctoluene  is  prepared  by  the  same  method  from  the 
corresponding  nitrotoluidine.  It  solidifies  in  a  freezing  mixture 
to  crystals  which  melt  at  16°;  it  boils  at  230°— 231°,  and  has  a 
specific  gravity  of  1168  at  220.1 

Paranitrotoluene  boils  at  238°,  and  on  the  gradual  evaporation 
of  its  alcoholic  or  ethereal  solution  separates  in  large,  thick 
rhombic  crystals  melting  at  54°. 

DlNITROTOLUENES,  C6H3  (N02)2,CH3. 

2025  Ordinary  Dinitrotoluene  (CH3  :  NO2  :  N02  =  l  :  2  :  4) 
was  obtained  by  Deville,  and  is  formed  by  the  further  nitration 
of  ortho-  and  para-nitrotoluene.  In  order  to  prepare  it,  toluene  is 
run  into  fuming  nitric  acid,  without  any  special  cooling,  until  oily 
drops  separate  out ;  the  mixture  is  then  allowed  to  cool,  and  an 
equal  volume  of  sulphuric  acid  gradually  added,  the  whole  being 
then  boiled  for  half  an  hour,  poured  into  snow,  and  the  precipi- 
tate recrystallized  from  hot  carbon  disulphide.2  It  crystallizes  in 
long,  monoclinic  needles,  which  melt  at  72°,  are  only  slightly 
soluble  in  cold  alcohol,  and  still  less  so  in  cold  carbon  disulphide, 
but  dissolve  readily  in  boiling  benzene. 

In  the  manufacture  of  dinitrotoluene  on  the  large  scale,  a 
liquid  by-product  is  obtained,  which  was  formerly  considered  to 
be  an  isomeric  dinitrotoluene.3  According  to  Glaus  and  Becker  it 
is  a  mixture  of  ordinary  dinitrotoluene,  orthodinitrotoluene,  and 
orthomononitrotoluene.4  Limpricht  found  that  1:2:5  dinitro- 
toluene is  also  contained  in  it ;  he  did  not  isolate  this  compound 
but  converted  it  into  the  corresponding  nitrotoluidine.5  Nolting 
and  Witt,  who  examined  a  larger  quantity  of  the  by-product, 
obtained  from  it  by  distillation  in  a  rapid  current  of  steam  40 
per  cent,  of  mononitrotoluenes,  consisting  of  almost  equal  parts 
of  the  para-  and  meta-compounds,  the  ortho-compound  being 

1  Beilstein  and  Kuhlberg,  Ann.  Chem.  Pharm.  clviii.  348. 

2  Ibid.  clvi.  13. 

3  Rosenstiehl,  Ann.  Chim.  Phys.  [4]  xxvii.  407.     Cunerth,  Ann.  Chem.  Pharm. 
clxxii.  222. 

4  Glaus  and  Becker,  Ber.  Deutsch.  Chem.  Ges.  xvi.  1590. 

5  Ibid,  xviii.  1400. 


TRINITROTOLUENES.  17 

present  only  in  very  small  amount.  Although  metanitrotoluene 
is  only  formed  to  a  small  extent  by  the  nitration  of  toluene, 
its  presence  in  comparatively  large  quantities  in  the  mixture  can 
be  readily  understood,  as  it  resists  the  further  action  of  nitric 
acid  much  more  strongly  than  its  isomerides;  it  therefore 
accumulates  in  the  by-product,  while  the  more  readily  attacked 
ortho-compound  almost  disappears.1 

Orthodinitrotoluene  (1:2:6)  can  best  be  obtained  pure  by  con- 
verting a-trinitrotoluene  into  dinitroparatoluidine,  and  replacing 
the  amido-group  of  this  by  hydrogen.  It  crystallizes  in  broad, 
golden  needles,  melting  at  60°— 61°.2 

Symmetric  Dinitrotoluene  (1  :  3  :  5)  may  be  prepared  from  the 
dinitroparatoluidine  which  melts  at  168°,  and  from  the  dinitro- 
orthotoluidine  melting  at  208°,  by  suspending  these  in  concen- 
trated nitric  acid  and  saturating  the  well-cooled  liquid  with 
nitrogen  trioxide ;  the  product  is  then  brought  in  small  portions 
at  a  time  into  eight  or  ten  parts  of  absolute  alcohol,  the  solution 
cooled  as  soon  as  the  evolution  of  nitrogen  has  ceased,  and  the 
dinitrotoluene  then  precipitated  with  water.  On  recrystallization 
from  -hot  water  it  is  obtained  in  small  needles,  whilst  it 
crystallizes  from  petroleum  spirit  in  small  prisms,  which  join  to 
form  chain-like  masses.  It  melts  at  92°  and  combines  with  benzene, 
forming  a  double  compound,  C7H6  (N02)2  -f-  C6H6,  crystallizing  in 
large  prisms  which  effloresce  in  the  air.3 

^-Dinitrotoluene.  Beilstein  and  Kuhlberg  obtained  this  com- 
pound by  agitating  metanitrotoluene  with  nitric  acid  of  specific 
gravity  1'54  for  a  long  time.  It  crystallizes  from  carbon 
disulphide  in  long  needles  melting  at  60°. 

TRINITROTOLUENES,  C6H2  (NO2)3  CH3. 

2026  a- Trinitrotoluene  (]  :  2  :  4  :  6)  is  formed  when  toluene4 
or  ordinary  dinitrotoluene5  is  heated  for  some  days  with  a  mixture 
of  nitric  and  sulphuric  acids.  It  may  be  more  rapidly  prepared 
by  dropping  toluene  into  a  mixture  of  pure  nitric  acid  and 
sulphuric  acid  containing  a  large  quantity  of  sulphur  trioxide 
and  warming  on  the  water-bath.6  It  is  very  slightly  soluble  in 

1  Claus  and  Becker,  Ber.  Deutsch.  Chem.  Ges.  xviii.  1336. 

2  Stiidel  and  Becker,  Liebig's  Ann.  ccxvii.  205  ;  Stadel,  ibid,  ccxxv.  384. 

3  Stadel,  Ber.  Deutsch.  Chew.  Gcs.  xiv.  901  ;  Liebiy's  Ann.  ccxvii.  189  ;  Hiibner, 
ibid,  ccxxii.  74  ;  Neville  and  Winther,  Ber.  Deutsch.  Chem.  Ges.  xvi.  2985. 

4  Wilbrandt,  Ann.  Chem.  Pharm.  cxxviii.  178. 

5  Tiemann,  Ber.  Deut-sch.  Chem.  Ges.  iii.  217. 

6  H.  Schmitt,  private  communication. 


18  AROMATIC  COMPOUNDS. 

cold,  more  readily  in  hot  alcohol,  from  which  it  crystallizes  in  large, 
rhombic  tablets  or  golden  needles  melting  at  82°.  On  heating 
with  ten  times  its  weight  of  fuming  nitric  acid  to  180°  it  is  con- 
verted into  symmetric  trinitrobenzene.1  When  aniline  is  added 
to  its  alcoholic  solution,  the  compound  C7H5(NO2)3  -f-  C6H7N 
is  obtained  in  long,  red,  lustrous  needles  melting  at  83° — 84°.2 

/3-  Trinitrotoluene.  Beilstein  and  Kuhlberg,  by  boiling  meta- 
nitrotoluene  with  nitric  and  sulphuric  acids,  obtained  a  tri- 
nitrotoluene, the  purity  of  which  they  doubted,  adding  that 
the  small  quantity  of  substance  obtained  by  them  was  probably 
a  mixture.  Hepp  then  proved  that  at  least  two  trinitrotoluenes  are 
formed  from  metanitrotoluene,  and  that  these  can  be  separated 
by  repeated  crystallization  from  alcohol  or  carbon  disulphide. 

/3-Trinitrotoluene,  which  is  only  formed  in  small  quantity,  is 
readily  soluble  in  carbon  disulphide,  slightly  in  cold,  more  readily 
in  hot  alcohol,  and  freely  in  ether  and  acetone.  It  crystallizes  on 
the  gradual  evaporation  of  its  solution  in  the  last-named  solvent 
in  transparent,  asymmetric  prisms  melting  at  112° ;  whilst  it 
separates  from  alcohol  in  dazzling  white  plates  or  flat  needles. 
On  heating  with  alcoholic  ammonia,  a  dinitrotoluidine  is  formed 
which  melts  at  94° ;  it  is  also  readily  attacked  by  aniline  and 
caustic  soda  solution. 

7- Trinitrotoluene  is  only  very  slightly  soluble  in  carbon  di- 
sulphide and  cold  alcohol,  and  separates  from  hot  alcohol  in  hard, 
compact,  yellowish  white  crystals,  while  it  crystallizes  from 
acetone  in  small,  hexagonal  tablets,  melting  at  104°. 

Concentrated  alcoholic  ammonia  converts  it,  even  in  the  cold, 
into  a  dinitrotoluidine,  melting  at  192°  — 193°. 

On  adding  aniline  to  a  hot,  alcoholic  solution  of  7-trinitro- 
toluene,  combination  does  not  occur  as  in  the  case  of  the 
symmetric  trinitrotoluene,  but  7-dinitrotolylphenylamine  is  ob- 
tained, diazo-amidobenzene  being  probably  simultaneously  formed: 

CH3.C6H2(N02)3 + 3C6H5.NH?  = 
CH3.C6H2(N02)2N(C6H6)H  +C6H6N2.NH.C6H6  +  2H2O. 

This  compound  forms  orange-coloured  needles  melting  at  142°. 

7-Trinitrotoluene  is  also  readily  attacked  by  caustic  soda  solu- 
tion, and  it  must,  therefore,  like  /3-trinitrotoluene  contain  two 
nitroxyls  in  adjacent  positions  (Part  III.  p.  92). 

1  Glaus  and  Becker,  Ber.  Deutsch.  Chem.  Ges.  xvi.  1596. 

2  Hepp,  Licbigs  Ann.  ccxv.  344. 


CHLOKONITROTOLUENES.  19 


CHLORONITROTOLUENES,  C6H3C1(NO2)CH3. 

2027  Parachlororthonilrotoluene  (4  :  2)  has  been  prepared  from 
ordinary  dinitrotoluene.  It  is  slightly  soluble  in  cold  alcohol, 
readily  volatilizes  with  steam,  and  crystallizes  in  needles  melting 
at  38°.  It  is  not  attacked  by  chromic  acid  solution.1 

Orthochloroparanitrotoluene  (2:4).  Wachendorff  obtained  this 
compound  by  heating  paranitrotoluene  with  antimony  chloride 
to  100°.  It  is  very  readily  volatile  in  steam,  dissolves  freely  in 
alcohol,  and  forms  long,  pointed  crystals  melting  at  64°— 65°. 
Potassium  permanganate  oxidizes  it  to  chloronitrobenzoic  acid.2 
Lellmann  has  converted  it  into  orthochlorotoluene'and  ortho- 
chlorobenzoic  acid.3 

WachendorfF  found  that  metanitrotoluene  could  not  be  chlori- 
nated. Wroblevsky,  by  the  action  of  nitric  acid  on  crude 
liquid  chlorotoluene  obtained  two  liquid  nitrochlorotoluenes ; 4 
Engelbrecht,  on  the  other  hand,  employing  crystalline  para- 
chloro toluene,  obtained  two  solid  compounds  which  he  was  unable 
to  separate  completely.5 

Parachlorometatoluene  (4  :  3)  has  been  prepared  from  meta- 
nitroparatoluidine  by  means  of  the  diazo-reaction,  and  is  identical 
with  one  of  Wroblevsky's  compounds.  It  is  a  strongly  refractive, 
golden-yellow  liquid,  which  boils  at  260°— 261°  and  solidifies  at 
a  low  temperature  to  yellow  needles  melting  at  7°.6 


BRO 

Br  :1 

2  • 

MO 

*p, 
5 

NITROTOLUENES,  C, 

,H3Br(N02).CH3.7 

Melting-point. 

.    .          76-3° 

2  : 

4 

needles    

.    .         74°—  75° 

3  : 

2 

3  : 

5 

prisms  8    

.    .             86° 

5  • 

2 

rhombic  crystals  ^ 

.    .             55° 

4  • 

2 

.    .              45°'5 

4  : 

3 

crystals                          .    . 

31°—  32° 

1  Beilstein  and  Kuhlberg,  Ann.  Chem.  Pharm.  clviii.  336. 

2  Ibid,  clxxxv.  273.  3  Ber.  Deutsch.  Chem.  Ges.  xvii.  534. 
4  Ann.  Chem.  Pkarm.  clxviii.  203.  5  Bcr.  Deutsch.  Chem.  Gcs.  vii.  797. 

6  Gattermaim  and  Kaiser,  ibid,  xviii.  2599. 

7  Neville  and  Winther,  ibid.  xiv.  417. 

8  Wroblevsky,  Ann.  Chem.  Pharm.  cxcii.  203. 

9  Grete,  ibid,  clxxvii.  246. 

10  Beilstein  and  Kuhlberg,  Hiibner  and  Roos,  Ber.  Deutsch.  Chem.  Ges.  vi.  799. 


20  AROMATIC  COMPOUNDS. 

TOLUENESULPHONIC   ACIDS. 

TOLUENEMONOSULPHONIC  ACIDS,  C6H4(SO3H).CH3. 

2028  By  the  action  of  fuming  sulphuric  acid  on  toluene, 
Deville  obtained  a  monosulphonic  acid  (Acide  sulfobenzotnique) 
in  small,  deliquescent  crystalline  plates,  and  prepared  some  of  its 
salts.  Later  researches  have  shown  that  in  this  way  toluene- 
parasulphonic  acid  is  formed  together  with  a  little  toluene-ortho- 
sulphonic  acid.1  If,  however,  concentrated  sulphuric  acid  be 
allowed  to  run  into  boiling  toluene,  only  the  para-acid  is  formed,2 
while  all  the  three  isomeric  sulphonic  acids,  together  with  their 
chlorides,  are  formed  by  the  action  of  chlorosulphonic  acid  on 
toluene : 3 

,01 

)H 
3  /OH 

+  S0,<          +2HC1. 
\S03H  S02C1  \OH 

The  product  is  poured  into  ice-cold  water,  the  chlorides 
separating  as  oily  liquids.  After  some  time  the  toluenepara- 
sulphonic  chloride  crystallizes  out  and  is  removed,  an  additional 
amount  of  this  being  obtained  by  repeatedly  cooling  the  liquid.  It 
is  then  purified  by  re-crystallization  from  pure  ether  and  decom- 
posed by  boiling  with  water.  The  liquid  chlorides  are  converted 
into  the  amides  by  treatment  with  ammonia,  and  these  are  then 
separated  by  fractional  distillation  and  converted  into  the  acids 
by  heating  with  hydrochloric  acid  to  140°— 150°.  The  ammo- 
nium salts  which  are  obtained  by  the  evaporation  of  the  solu- 
tions are  converted  into  the  barium  salts,  from  which  either  the 
free  acids  or  other  salts  can  be  prepared.  The  aqueous  solution 
from  which  the  chlorides  have  been  separated  is  treated  with 
milk  of  lime,  the  calcium  salts  of  the  acids  being  thus  formed ; 
the  potassium  salts  are  prepared  from  these,  converted  into  the 
sulphonic  chlorides  by  the  action  of  phosphorus  pentachloride 
and  these  separated  as  just  described. 

1  Engelhardt  and  Latschinow,  Zcitschr.  Chcm.  1869,  67. 

2  Chrustschow,  Ber.  Dcutsch.  Chem.  Ges.  vii.  1167. 

3  Claesson  and  Wallin,  ibid.  xii.  1848  ;  Claesson,  ibid.  xvii.  Ref.  283. 


TOLUENESULPHONIC  ACIDS.  21 

The  meta-  and  ortho-sulphonic  acids  can  also  be  obtained  from 
the  three  toluidines,  which  are  converted  by  fuming  sulphuric 
acid  into  the  following  sulphonic  acids  : 

GH-3 


H 
±i 

\  /S03H  \/NH2  \/'S03H. 


The  toluenesulphonic  acids  are  then  obtained  from  these  by 
replacing  the  amido-group  by  hydrogen  ;  they  can  also  be  pre- 
pared by  the  action  of  sulphur  dioxide  on  the  diazo-compounds 
of  the  toluidines  :  l 


C6H4<  +  S0.2  +  H20  =  C6H  +HC1+N2. 

XN  —  NCl  \302.OH. 

Tolueneparasulphonic  acid,  C6H4(CH3)S03H+  H20,  crystallizes 
in  thick  deliquescent  tablets  or  flat  prisms. 

Tolueneparasulphonic  chloride,  C6H4(CH3)S02C1,  crystallizes 
from  ether  in  rhombic  tablets,  and  is  only  slowly  decomposed  by 
water. 

Tolueneparasulphonamide,  C6H4(CH3)S02.NH2,  forms  small 
crystalline  plates  melting  at  136°,  which  are  slightly  soluble  in 
water,  more  readily  in  alcohol.  A  solution  of  this  compound  in 
the  necessary  amount'  of  caustic  potash  yields  on  evaporation  a 
residue  from  which  alcohol  extracts  the  compound  C6H4(CH3) 
S02.NHK+H20,  crystallizing  in  needles.2 

Toluenemetasulphonic  acid,  C6H4(CH3)S03H  +  H20,  forms  very 
deliquescent,  thin  crystalline  crusts. 

Toluenemetasulphonic  chloride,  C6H4(CH3)S02C1,  is  an  oily 
liquid. 

Toluenemetasulphonamide,  C6H4(CH3)S02.NH2,  crystallizes  in 
long  plates  melting  at  107°-108°. 

Toluene-orthosulphonic  acid,  C6H4(CH3)S03H+2H2O,  forms  thin 
deliquescent  plates  ;  the  chloride  is  an  oily  liquid,  and  the  amide 
crystallizes  in  quadratic  pyramids  or  prisms,  which  are  almost 
insoluble  in  cold  water,  and  only  slightly  soluble  in  alcohol. 

The  salts  of  the  three  acids  as  a  rule  crystallize  well  (Claesson 
and  Wallin). 

1  Miiller,  Per.  Deutsch.  Chem.  Gcs.  xii.  1348. 

2  Hakansson,  ibid.  v.  1084  ;  Claesson  and  Berg,  Hid.  xiii.  1170. 

233 


22  AROMATIC  COMPOUNDS. 

TOLUENEDISULPHONIC  ACIDS,  C6H3(CH3)(S03H)2. 

2029  a-Toluenedisulphonic  acid  (CH3 :  S03H :  S03H=1 : 2  : 4), 
is  a  thick  liquid  which  can  be  heated  above  100°  without  de- 
composition ;  it  may  be  prepared  by  heating  toluene,  or  its  ortho- 
and  para-sulphonic  acids  with  fuming  sulphuric  acid,1  as  well  as 
by  passing  toluene  vapour  into  concentrated  sulphuric  acid 
heated  to  2400.2  Its  amide,  C6H3(CH3)(S02.NH2)2  is  tolerably 
soluble  in  warm  water,  and  crystallizes  in  prisms  melting  at 
185° -186°. 

Senhofer  and  Forber,  by  heating  toluene  with  a  mixture  of 
sulphuric  acid  and  phosphorus  pentoxide,  obtained  a  7-toluene- 
sulphonic  acid,3  which  is,  according  to  Claesson,  identical  with 
the  a-acid.4 

j3-Toluenedisulphonic  acid  is  obtained  in  small  quantities  in 
the  preparation  of  the  a-compound,  and  is  also  formed  when 
toluenemetasulphonic  acid  is  treated  with  fuming  sulphuric  acid 
(Hakansson).  Its  amide  melts  at  224°  (Claesson). 

y-Toluenedisulphonic  acid  (1:3:  5).  When  orthotoluidine  is 
heated  with  fuming  sulphuric  acid  or  with  chlorosulphonic  acid, 
toluidinedisulphonic  acid  (CH3  :  NH2 :  SO3H  :  SO3H  =  1:2:3:5) 
is  formed ;  this  yields  a  crystalline  diazo-compound,  CH3.C6H2 
(N2S03)S03H,  which  is,  according  to  Neville  and  Winther,  con- 
verted into  the  toluenedisulphonic  acid  by  heating  with  absolute 
alcohol  under  pressure,5  while  Limpricht  and  Hasse  observed 
that  ethoxytoluenedisulphonic  acid,  CH3.C6H2(OC2H5)(S03H)2 
is  thus  formed.  In  order  to  obtain  the  former,  the  diazo-com- 
pound is  converted  into  iodotoluenedisulphonic  acid,  and  this 
heated  with  concentrated  hydriodic  acid. 

7-Toluenedisulphonic  acid  forms  an  amide  which  crystallizes  in 
small  lustrous  plates  melting  above  2400.6 


TOLUENETRISULPHONIC  ACIDS,  C6H2(CH3)(S03H)3. 

Only  one  of  the  six  toluenetrisulphonic  acids  which  are  theo- 
retically possible  is  known ;  it  is  obtained  by  gradually  heating 

1  Hakansson,  Ber.  DeiUsch.  Chem.  Ges.  v.  1084 ;  Claesson  and  Bey,  ibid.  xiii. 
1170. 

2  Gnehm,  ibid.  x.  542  ;  see  also  Fahlberg,  ibid.  xii.  1052. 
8  Ann.  Chem.  Pharm.  clxiv.  226. 

4  Ber.  Deutsch.  Chem.  Ges.  xvii.  Ref.  284. 

5  Ibid.  xv.  2993.  6  Ibid,  xviii.  2177. 


THE  CRESOLS.  23 


potassium  a-toluenedisulphonate  with  three  molecules  of  chloro- 
sulphonic  acid  to  24-0°,  until  the  product  forms  a  clear  solution 
in  water.  The  barium  salt  is  then  prepared,  and  from  this 
the  potassium  salt,  which  is  converted  by  the  action  of  phos- 
phorus pentachloride  into  toluenetrisulphonic  chloride,  C6H2 
(CH3)(SO2C1)3,  which  crystallizes  from  chloroform  in  rhombic 
tablets  melting  at  153°.  On  heating  with  water  to  130° -140° 
the  free  acid  is  obtained ;  it  crystallizes  with  six  molecules  of 
water  in  long,  fine  needles.1 


MONOHYDROXYTOLUENES  AND  ALLIED 
BODIES. 

CH3 
THE  CRESOLS,  C6H 


2030  In  1851  Stadeler  discovered  in  the  urine  of  the  cow, 
together  with  phenylic  acid,  a  very  similar  body  which  he  named 
Taurylic  acid,  and  considered  to  be  the  next  higher  homologue  of 
phenylic  acid.2  As  the  question  was  subsequently  raised  whether 
the  creosote  discovered  by  Reichenbach  in  wood-tar  is  identical 
with  phenol  or  not,  Fairlie,  under  Williamson's  directions,  con- 
ducted an  investigation  on  the  so-called  coal-tar  creosote  (Part 
III.  p.  70)  and  found  in  it  "  hydrate  of  cresyl"  C7H80,  the 
homologue  of  phenyl  hydrate  ;  he  describes  this  compound  as  a 
strongly  refractive  liquid  smelling  like  phenol  and  boiling  at 
203°,  and  investigated  its  properties  with  some  care.3  Duclos 
discovered  the  same  compound  in  tar  from  pine-wood4  and 
Marasse  in  that  from  beech-wood.5 

Griess  obtained  cresol  or  cresyl  alcohol  artificially  by  boiling 
diazotoluene  nitrate  with  water,6  and  Wurtz  by  fusing  toluene- 
sulphonic  acid  with  caustic  potash.7 

Engelhardt  and  Latschinow  were  the  first  to  prove  that  three 
isomeric  cresols  exist  ;  they  obtained  pure  paracr"esol,  or,  as 
they  called  it,  a-cresol,  by  fusing  tolueneparasulphonic  acid  with 
caustic  potash,  and  from  ordinary  toluidine  by  Griess'  reaction. 
By  the  same  reactions  they  prepared  /3-cresol  from  the  ortho- 

1  Claesson,  Ber.  Deutsch.  Chem.  Ges.  xiv.  307. 

2  Ann.  Chem.  Pharm.  Ixxvii.  188. 

8  Chem.  Soc.  Journ.  vii.  232.  *  Ann.  Chem.  Pharm.  cix.  135. 

6  Ibid.  clii.  64.  6  Jahresber.  1866,  458. 

7  Ann.  Chem.  Pharm.  cxliv.  121. 


24  AROMATIC  COMPOUNDS. 

sulphonic  acid  and  pseudotoluidine  (orthotoluidine),  but  they 
did  not  obtain  it  in  a  pure  state.  They  further  found  that 
thymol,  C6H3(CH3)(C3H7)OH,  on  heating  with  phosphorus  pent- 
oxide,  decomposes  into  propylene  and  7-cresol.1  This  metacresol 
was  then  obtained  in  larger  quantities  by  Oppenheim  and  Pfaff 
by  heating  hydroxyuvitic  acid  with  lime.2 

Kekul4  obtained  pure  orthoeresol  by  acting  with  nitrous  acid 
on  orthotoluidine  and  by  heating  carvacrol  (cymophenol),  an 
isomeride  of  thymol,  with  phosphorus  pentoxide.3 

The  constitution  of  the  three  cresols  was  determined  with 
certainty  by  Barth,  who  showed  that  on  fusion  with  caustic 
potash,  orthoeresol  is  oxidized  to  salicylic  acid,  metacresol  to 
hydroxybenzoic  acid,  and  paracresol  to  parahydroxybenzoic  acid 
(Part  III.  p.  45).4 

Further  investigations  have  shown  that  the  cresol  contained 
in  coal-tar  is  a  mixture  of  the  three  isomerides.5  It  is  obtained 
from  the  oily  mother-liquor  left  after  crystallization  of  the 
phenol  by  dissolving  in  caustic  soda,  removing  all  naphthalene 
by  a  current  of  steam,  and  then  fractionally  precipitating  the 
solution  with  hydrochloric  acid ;  the  cresol  separates  out  first, 
the  phenol,  being  a  stronger,  acid,  remaining  in  solution.6  Ac- 
cording to  another  method,  the  solution  is  neutralized  with 
hydrochloric  acid  and  the  mixture  agitated  with  sufficient 
baryta  water  to  dissolve  all  the  phenol.7  The  cresol  obtained 
is  purified  by  distillation  until  it  boils  at  198°  — 203°.  Deriva- 
tives of  all  three  cresols  can  be  prepared  from  it,  but  only  the 
para-compound  can  actually  be  extracted  in  the  pure  condition. 
This  is  effected  by  treating  the  mixture  with  benzoyl  chloride, 
paracresyl  benzoate,  melting  at  78°,  being  formed ;  this  is  sepa- 
rated by  pressing  from  the  liquid  ethers  of  the  two  other  cresols, 
purified  by  re-crystallization,  and  decomposed  by  caustic  soda 
(Engelhard t  and  Latschinow).  Baumann  has  pointed  out  that 
the  cresol  (taurylic  acid)  contained  in  the  urine  of  graminivora 
occurs  as  the  potassium  salt  of  paracresylsulphuric  acid.8  This 
compound  also  occurs  in  human  urine  during  scarlatina,  ery- 
sipelas, &c.9  The  urine  of  horses  also  contains  some  orthocresyl 

Zeitschr.  Chem.  1869,  618. 

Bcr.  Dcutsch.  Chem.  Gcs.  viii.  884. 

Ibid.  vii.  1006. 

Ann.  Chem.  PJwtrm.  cliv.  356. 

Schotten  and  Tiemann,  ibid.  xi.  783. 

Muller,  Zeitschr.  Chem.  1865,"  27?. 

Ihle,  Journ.  PraJct.  Chem.  [2]  xiv.  442. 
8  Ber.  Dcutsch.  Chem.  Ges.  ix.  1389,  1716. 
8  Brieger,  Hoppe-Seyler's  Zeitschr.  iv.  204. 


ORTHOCRESOL.  25 


sulphuric  acid.1  Para-  and  ortho-cresol  are  also  formed  when 
the  liver  of  fche  horse  is  caused  to  putrefy  with  the  addition  of 
river-mud.2 

2031  Orthocresol  is  best  obtained  by  adding  12  parts  of  pure 
potassium  nitrite  to  a  solution  of  15  parts  of  orthotoluidine  and 
15  parts  of  sulphuric  acid  in  500  parts  of  water ;  the  liquid  is 
heated  by  a  current  of  steam,  and  the  cresol  distilled  off  in  the 
steam.3  It  forms  colourless  crystals,  melts  at  30°  and  boils  at 
188°.  Its  aqueous  solution  is  coloured  blue  by  ferric  chloride ; 
on  fusion  with  caustic  potash  it  is  oxidized  to  salicylic  acid. 
When  administered  to  a  dog  it  appears  in  the  urine  as  ortho- 
cresylsulphuric  acid  and  oxycresylsulphuric  acid  (hydrotolu- 
quinonesulphuric  acid).  By  the  action  of  potassium  chlorate 
and  hydrochloric  acid  it  yields  di-  and  tri-chlorotoluquinone.4 

Orthocresyl  oxide,  (CH3.C6H4)2O.  If  a  few  grains  of  iodine  and 
then  some  aluminium  are  added  to  boiling  orthocresol,  alu- 
minium orthocresylate,  (CH3.C6H40)GA12,  is  formed,  and  this 
solidifies  on  cooling  to  a  black  vitreous  mass.  When  subjected 
to  dry  distillation  it  yields,  among  other  products,  orthocresol 
and  orthocresyl  oxide,  which  is  a  colourless  liquid  smelling  like 
the  geranium,  and  boiling  at  272°- 278°. 5 

Dichlororthocresol,  C6H2C12(CH3).OH,  is  obtained  by  the  action 
of  chlorine  on  boiling  orthocresol ;  it  crystallizes  from  alcohol  in 
needles  with  a  silky  lustre,  melts  at  55°  and  on  oxidation  under- 
goes partial  combustion,  at  the  same  time  yielding  trichloro- 
toluquinone.6 

Bromorfkocresol,  C6H3Br(CH3)OH,  has  been  prepared  from 
bromorthotoluidine,  and  crystallizes  from  alcohol  in  lustrous 
golden  needles  melting  at  88' 5°.7 

a-Nitro-orthocresol,  C6H3(CH3)  (N02)  OH  (1:3:  2),  is  formed 
when  a  solution  of  2  parts  of  orthocresol  in  2  parts  of  glacial 
acetic  acid  is  allowed  to  drop  into  a  cold  mixture  of  3  parts  of 
nitric  acid,  of  specific  gravity  1'4,  and  6  parts  of  glacial  acetic 
acid.  It  is  insoluble  in  water  and  crystallizes  from  dilute 
alcohol  in  long,  yellow  prisms  melting  at  69 '5°.  Its  potassium 
salt  crystallizes  in  garnet-red,  rhombic  tablets. 

When  the  hydrochloride  of  the   amidocresol   obtained   from 

Preusse,  ibid.  ii.  355  ;  Bcr.  Deutsch.  Chem.  Gcs.  xi.  1911. 
Baumann  and  Brieger,  Hoppe-Seyler's  Zcitschr.  iii.  149,  252. 
Schotten  and  Tiemann,  loc.  cit. 
Southworth,  Ann.  Chem.  Pharm.  clxviii.  273. 
Gladstone  and  Tribe,  Journ.  Chem.  Soc.  1886,  i.  25. 
Glaus  and  Riemann,  Ber.  Deutsch.  Chem.  Ges.  xvi.  1598. 
7  Wroblevsky,  Ann.  Chem.  Pharm.  clxviii.  165. 


AROMATIC  COMPOUNDS. 


this  compound  is  distilled  with  sodium  formate,  a  methenyl 
compound  is  formed ;  this  reaction  is  characteristic  of  all  the 
amidophenols  in  which  the  amido-group  is  in  the  ortho-relation 
to  the  hydroxyl.1 

Methenylamidorthocresol  is  formed  according  to  the  following 
equation  : 

/NH2  -N 

CH3.C6H8/          +  CHO.OH  =  CH3.C6H3<      >CH+2H20. 


It  is  a  crystalline  mass  which  melts-  at  38°— 39°,  boils  at  200° 
and  has  a  peculiar  smell,  resembling  that  of  acetamide,  charac- 
teristic of  these  anhydro-bases. 

A  liquid  nitrocresol  boiling  at  226° — 230°  is  formed  together 
with  the  solid  compound.2 

fi-Nitro-ortJiocresol  (1:5: 2)  is  prepared  from  the  corresponding 
nitro-orthotoluidine  by  means  of  the  diazo-reaction  or  by  heating 
it  with  strong  caustic  soda.  It  crystallizes  in  fine,  light  yellow 
needles  and  melts  at  95°.3  On  reduction  it  yields  fi-amido- 
orthocresol,  the  hydrochloride  of  which  crystallizes  readily. 

<y-Nitro-OTthocresol  (1:4: 2)  is  formed  together  with  the  a-com- 
pound  when  orthocresol  is  nitrated  at  as  low  a  temperature  as 
possible.  On  distillation  with  steam  it  remains  behind.  It  is 
only  very  slightly  soluble  in  water,  readily  in  alcohol  and  ben- 
zene, and  crystallizes  in  white  needles  united  to  form  bushy 
aggregates,  or  in  small,  hexagonal  tablets,  being,  therefore, 
dimorphous  like  paranitrophenol.  It  melts  at  82° — 85°,  and 
forms  a  potassium  salt,  crystallizing  in  small  brass-yellow 
plates.  On  reduction  it  is  converted  into  y-am'ido-orthophenol, 
crystallizing  in  tablets  which  have  a  silvery  lustre  and  melt  at 
175°.  When  oxidized  in  an  acid  solution,  it  is  converted  into 
toluquinone.  Hirsch  has  been  unable  to  obtain  the  liquid  nitro- 
cresol mentioned  above.4 

Dinitro-orthocresol,  C6H2  (CH3)  (NO2)2  OH  (1 :  3  :  5  :  2),  was 
first  obtained  from  orthotoluidine,  nitro-orthotoluidine  (NH2 : 
NO2  =  2 :  5),  and  orthotoluidinesulphonic  acid  (NH2 :  S03H =2:3), 
by  converting  them  into  diazo-compounds  and  heating  these  with 
dilute  nitric  acid.5  It  is  also  formed  by  the  further  nitration  of 

Ladenburg,  Per.  Deutsch.  Chem.  Gfes.  ix.  1524;  x.  1124. 

Hofmann  and  Miller,  ibid.  xiv.  467. 

Neville  and  Winther,  ibid.  xv.  2978. 

Hirsch,  ibid,  xviii.  1511. 

Neville  and  Winther,  ibid.  xiii.  1496  ;  Nblting,  and  Salis,  ibid.  xiv.  987. 


METACRESOL.  27 


a-  and  <y-nitro-orthocresol  (Hirsch),  and  of  orthocresyl  ether.' 
It  crystallizes  from  alcohol  in  long,  yellow  prisms,  and  from 
petroleum-spirit  in  broad,  golden-yellow  needles,  which  have  a 
blue  surface-lustre  and  melt  at  86°. 

On  the  reduction  of  its  ethyl  ether  the  diamido- ether  is 
obtained,  and  this  compound  forms  a  chrysoidine  with  diazo- 
benzene  (Part  III.  p.  301),  thus  affording  a  further  proof  that  the 
nitroxyl  groups  in  dinitrocresol  have  the  meta-relation  to  each 
other. 

2032  Metacresol.  In  order  to  prepare  this  compound,  100 
grammes  of  thymol  are  heated  for  ten  or  twelve  hours  with  35 
grammes  of  phosphorus  pentoxide,  the  propylene  which  is 
evolved  being  passed  into  bromine  in  order  to  obtain  its  bromide 
as  a  by-product.  The  syrupy  mass  is  brought  into  115 — 120 
grammes  of  fused  caustic  potash,  and  the  mixture  kept  in  a 
state  of  fusion  and  well  agitated  for  five  or  ten  minutes.  It  is 
then  dissolved  in  water  and  extracted  with  ether  in  order  to 
remove  cresyl  phosphate  and  other  substances ;  the  residue  is 
then  decomposed  with  hydrochloric  acid,  the  metacresol  taken 
up  with  ether,  the  latter  distilled  off,  and  the  product  purified 
by  distillation  in  a  current  of  carbon  dioxide  (Schotten  and 
Tiemann). 

It  is  a  liquid  which  smells  like  phenol,  boils  at  201°  and  does 
not  solidify  in  a  freezing  mixture ;  if,  however,  a  crystal  of  phenol 
be  thrown  into  the  cooled  liquid  it  solidifies  immediately,  form- 
ing crystals  resembling  those  of  phenol  and  melting  at  3° — 4°.2 
Its  aqueous  solution  is  coloured  violet  to  blue  by  ferric  chloride ; 
by  the  action  of  potassium  chlorate  and  hydrochloric  acid,  it  is 
converted  into  dichlorotoluquinone  (South worth). 

Metacresyl  oxide,  (CH3.C6H4)2O,  is  formed,  together  with  pro- 
pylene and  other  products  by  the  dry  distillation  of  aluminium 
thymol,  (C3H7(CH3)C6H3O)6A1<,,  and  is  a  liquid  boiling  at 
284°— 2880.3 

Bromometacresol,  C6H2Br(CH3)OH  (1  :  3  : 5),  has  been  pre- 
pared from  the  corresponding  bromotoluidine,  and  crystallizes 
from  hot  water  in  white  needles  melting  at  56° — 57°.4 

Nitrometacresol,  C6H3(CH3)(N02)OH  (1:3:  5),  is  prepared 
from  symmetric  dinitrotoluene  ;  it  crystallizes  from  hot  water  in 
light  yellow,  lustrous  prisms,  containing  one  molecule  of  water 


1  Stadel,  Ann.  Chem.  Pharm.  ccxvii.  158. 

2  Stadel,  Ber.  Deutsch.  Chem.  Ges.  xviii.  3443. 

3  Gladstone  and  Tribe,  Journ.  Chem.  Soc.  1882,  i.  5. 

*  Neville  and  Winther,  Ber.  Deutsch.  Chem.  Ges.  xv.  2991. 


28  AROMATIC  COMPOUNDS. 

of  crystallization.  It  is  deposited  from  solution  in  benzene  in 
anhydrous  crystals  melting  at  90° — 91°.  On  reduction  it  yields 
amidometacresol,  the  hydrochloride  of  which  is  readily  soluble.1 

Trinitrometacresol,  C6H(NO2)3(CH3)OH  (N02 :  N02 :  NO2  =  2  : 
4:6),  was  obtained  by  Duclos  from  crude  cresol ;  N  biting  and  Salis 
have  prepared  it  from  metacresol,  which  is  readily  converted  into 
the  trinitro-compound,  while  its  isomerides  yield  the  dinitrocresols 
as  final  products.  In  order  to  prepare  it,  coal-tar  cresol  is 
dissolved  in  3  parts  of  concentrated  sulphuric  acid,  and  allowed 
to  stand  in  a  warm  place  until  cresol  no  longer  separates  out  on 
the  addition  of  water.  Crude  nitric  acid  is  then  gradually 
added  to  the  aqueous  solution,  which  is  subsequently  evaporated, 
the  residue  being  extracted  with  a  little  water  to  remove  picric 
and  oxalic  acids,  and  repeatedly  re-crystallized  from  alcohol.2 

Liebermann  and  van  Dorp  obtained  it  by  heating  nitrococ- 
cussic  acid,3  C6(N02)3(CH3)(C02H)OH,  and  Emmerling  and 
Oppenheim  by  the  action  of  nitric  acid  on  hydroxyuvitic  acid, 
C6H2(CH3)(C02H)  OH.4  Trinitrometacresol  is  slightly  soluble 
in  cold,  somewhat  more  readily  in  hot  water,  and  crystallizes  in 
long,  yellow  needles  melting  at  105° — 106°. 

When  its  ethyl  ether  is  heated  with  alcoholic  ammonia,  no 
nitrous  acid  is  removed  (Nolting  and  Salis),  which  proves  that  it 
contains  no  nitroxyl  groups  in  the  ortho-relation  (Part  III. 
p.  63),  and,  therefore,  that  trinitrometacresol  has  the  following 
constitution  : 

CH3 

NO/NNO, 

H\/OH 

N02 

2033  Paracresol  is  most  readily  obtained  from  paratoluidine,  as 
orthocresol  is  from  orthotoluidine ;  it  crystallizes  in  prisms  melting 
at  36°,  and  boils  at  198° ;  its  aqueous  solution  is  coloured  blue 
by  ferric  chloride.  It  differs  from  its  isomerides  in  not  yielding 
a  chlorinated  toluquinone  by  the  action  of  potassium  chlorate  and 
hydrochloric  acid. 

Paracresyl  oxide  (CH3.C6H4)20,  has  been  prepared  by 
Gladstone  and  Tribe  in  the  same  mariner  as  the  ortho-compound, 

1  Bcr.  Deutsch.  Chtm.  Ges.  xv.  2978. 

2  Beilstcin  and  Kellner,  Ann.  Chem.  Pharm.  cxxviii.  165. 
8  Ibid,  clxiii.  101. 

4  Ber.  Deutsch.  Chem.  Ges.  ix.  1094. 


PARACRESOL.  29 


and  is  also  formed  by  heating  paracresol  to  300°  with  zinc  chloride. 
It  crystallizes  from  alcohol  in  small  lustrous  plates,  and  from 
petroleum  spirit  in  needles  which  have  a  silky  lustre,  and  melt 
at  165°,  but  readily  volatilize  at  1000.1 

Chloroparacresol,  C6H3(CH3)C1(OH)  (1:3:  4),  is  formed  by 
the  action  of  dry  chlorine  on  anhydrous  sodium  paracresate.  It 
is  a  colourless  liquid  which  boils  at  195° — 196°,  and  has  a  peculiar, 
unpleasant,  persistent  odour.  Phosphorus  pentachloride  converts 
it  into  a  dichlorotoluene,  which  yields  on  oxidation  the  ortho- 
dichlorobenzoic  acid  melting  at  2000.2 

Dichloroparacresol,  C6H2(CH3)C12.OH,  is  formed  by  the 
action  of  chlorine  on  boiling  paracresol ;  it  crystallizes  from 
alcohol  in  monoclinic  needles,  and  from  a  hot,  concentrated 
solution  in  petroleum-ether  in  long  needles  melting  at  39° ;  on 
the  gradual  evaporation  of  a  dilute  solution,  it  is  obtained  in 
transparent  prisms  with  a  melting  point  of  42° ;  these,  however, 
soon  fall  to  pieces,  and  the  product  then  melts  at  39°.  On 
oxidation  the  dichlorobenzoic  acid  melting  at  156°  is  formed 
(Glaus  and  Riemann). 

Bromoparacresol,  C6H3(CH3)Br(OH)  (1:3:  4),  is  obtained 
by  the  action  of  bromine  on  potassium  paracresate.  It  is  a 
liquid  which  does  not  solidify  in  a  freezing  mixture,  boils  at 
213° — 214°,  and  has  a  less  unpleasant  smell  than  the  chlorine 
compound  (Schall  and  Dralle). 

Bromoparacresol  (1 :  2 :  4)  may  be  readily  obtained  by  the 
action  of  bromine  on  a  solution  of  paracresol  in  chloroform  ;  it 
crystallizes  in  needles,  melting  at  17° — 18°,  and  boils  at 
218° — 220°.  On  fusion  with  caustic  potash  it  is  converted  into 
lutorcinol,  C6H3  (CHS)  (OH)2.3 

Dibromoparacresol,  C6H2(CH3)Br2(OH),  is  also  formed  when 
potassium  paracresate  is  treated  with  bromine.  It  crystallizes 
from  alcohol  in  prisms  which  are  isomorphous  with  dichloropara- 
cresol  and  melt  at  49°  (Schall  and  Dralle). 

lodoparacresol,  C6H3(CH3)I(OH)  (1:3:  4),  is  an  oily  liquid, 
and  is  obtained  by  the  action  of  iodine  on  potassium  paracresate  ; 
on  fusion  with  potash  it  yields  protocatechuic  acid,  C6H3(OH)2 
C02H,  and  catechol. 

Di-iodoparacresol,  C6H2(CH3)I2(OH),  is  formed  in  the  pre- 
paration of  the  mono-compound,  and  crystallizes  in  small  tablets 
melting  at  61'5°  (Schall  and  Dralle). 


1  Buch,  Ser.  Deutsch.  Chem.  Ges.  xvii.  2638. 

3  Schall  and  Dralle,  ibid.  xvii.  2528.         3  Vogt  and  Henninger,  ibid.  xv.  1081. 


30  AROMATIC  COMPOUNDS. 

a-Nitroparacrcsol,  C6H3(CH3)(N02)OH  (1:3:  4),  is  obtained 
by  boiling  nitracetparatoluide  with  caustic  soda,1  and  by  the 
nitration  of  paracresol.2  It  is  slightly  soluble  in  water,  readily 
in  alcohol,  and  crystallizes  in  flat,  yellow  needles,  which  melt  at 
33*5°,  and  are  volatile  in  steam. 

a-Amidoparacresol,  C6H3(CH3)(NH2)OH  (1:3:4)  is  formed 
by  the  reduction  of  the  nitro-compound  with  tin  and  hydro- 
chloric acid ;  it  crystallizes  from  ether  in  monoclinic  prisms,  and 
when  heated  with  formic  acid  yields  methenylamidoparacresol, 
melting  at  45°  (Hofmann  and  Miller). 

/3-Nitroparacresol,  (CH3 :  NO2 :  OH  =  1 :  2  :  4),  is  prepared  from 
ordinary  dinitrotoluene  by  reducing  it  with  ammonium  sulphide 
to  nitrotoluidine  and  then  replacing  the  amido-group  by  hy- 
droxyl.  It  forms  long  yellow  crystals  which  melt  at  78°  and  are 
readily  soluble  in  hot  water  and  alcohol.3 

(3-Amidoparacresol,  (CH3  :  NH2 :  OH  =1:2:4),  is  obtained 
by  the  reduction  of  the  preceding  compound,  and  crystallizes 
from  hot  water  in  small  plates  melting  at  143° — 1440.4 

y-Amidoparacresol,  (CH3 :  NH2 :  OH  =  1 : 4  : 2).  The  hydro- 
chloride  of  this  base  is  obtained  by  converting  the  monacetyl 
compound  of  the  corresponding  diamidotoluene  into  acetamido- 
cresol,  C6H3(CH3)OH(NH.C2H30)  and  boiling  this  with  hydro- 
chloric acid.  It  crystallizes  in  small  glistening  plates,  and  on 
treatment  with  potassium  bicarbonate  yields  the  free  base, 
which  forms  small  lustrous  plates  or  needles,  melting  at 
159°— 161°  (Wallach). 

The  constitution  of  the  substituted  paracresols  follows  from 
their  conversion  into  dihydroxytoluenes. 

Dinitroparacresol,  C6H2(CH3)(NO2)2OH(1 :3  :5  :4),  has  been 
prepared  from  the  corresponding  dinitrotoluidine  and  by  the 
nitration  of  cresolsulphonic  acid.5  It  is  also  obtained  by  warming 
the  diazo-compound  prepared  from  paratoluidinesulphonic  acid 
with  nitric  acid  (Neville  and  Winther),  and  by  the  nitration  of 
paracresol  ethyl  ether;  it  crystallizes  from  dilute  alcohol  in 
yellow  needles  melting  at  85°.  On  the  reduction  of  its  ethyl 
compound,  diamidoparacresyl  ether,  C6H2(CH3)(NH2)2OC2H6,  is 

1  Wagner,  Ber.  Deutsch.  Chem.  Ges.  vii.  537 ;  Neville  and  Winther,  ibid.  xv. 
2893. 

2  Armstrong  and  Thorpe,  Jahresb.  Chem.  1876,  452  ;  Hofmann  and  Miller, 
loc.  cit. 

3  Knecht,  Ann.  Chem.  Pharm.  ccxv.  83  ;  Ber.  Deutsch.  Chem.  Ges.  xv.  298. 
Neville  and  Winther,  ibid.  xv.  2980. 

4  Wallach,  ibid.  xv.  2831. 

5  Armstrong  and  Field,  Ber.  Deutsch.  Chem.  Ges.  vi.  974. 


DIHYDROXYTOLUENES.  31 

obtained  ;  this  compound  forms  a  chrysoidine  with  diazobenzene 
chloride,  proving  that  the  nitroxyls  of  the  dinitrocresol  are  in 
the  meta-relation  to  each  other. 

Potassium  dinitroparacresate,  C6H2(CH3)(NO2)2OK,  crystallizes 
in  red  needles  and  forms  the  "golden  yellow,"  which  was 
exhibited  as  a  new  dye  in  the  Belgian  section  of  the  Vienna 
Exhibition  in  1873.1 

It  is  also,  together  with  the  potassium  salt  of  dinitro-ortho- 
cresol,  contained  in  "  safronsurrogate,"  which  is  used  for  colouring 
milk,  butter,  and  cheese.2 

Victoria  yellow  or  aniline  orange,  which  formerly  came  into 
the  market  as  a  red  powder,  is  the  salt  of  a  third  dinitrocresol, 
the  constitution  of  which  is  unknown.  It  crystallizes  from  hot 
water  in  yellowish  needles,  melting  at  109° — 1100.3 

Thiocresols,  C6H4(CH3)SH,  are  obtained  by  the  reduction  of 
the  corresponding  sulphonic  chlorides. 

Melting-  Boiling- 
point,     point. 
Orthothiocresol 4     small,  delicate  plates  .       15°     188° 

Metathiocresol 5      liquid —      188° 

Parathiocresol 6       large  plates 43°     189° 


DIHYDROXYTOLUENES  AND    ALLIED   BODIES. 

HOMOCATECHOL,  OR  HOMOPYROCATECHIN,  C6H3(CH3)(OH)2 

(1:3:4). 

2034  Hugo   Miiller  obtained  this  compound    by  heating  its 
monomethyl  ether,  creosol,  with  hydriodic  acid  : 7 


6 

It  is  also  formed  by  fusing  creosol  with  caustic  potash,8  by 
boiling  the  diazo-compound  of  a-amidocresol  with  water  (Neville 

1  Piccard,  Ber.  Deutsch.   Chem.   Ges.  viii.  685 

2  Wichelhaus,  ibid.  vii.  770. 

8  Martius  and  Wichelhaus,  ibid.  ii.  206. 

4  Hiibner  and  Post,  Ann.  Chcm.  Pharm.  clxix.  30. 

5  KM-  «  Marcker,  ibid,  cxxxvi.  79. 

7  Chem.  News,  x.  269. 

8  Tiemann  and  Koppe,  Ber.  Deutsch.  Chem.  Ges.  xiv.  2025. 


AROMATIC  COMPOUNDS. 


and  Whither),  and  by  submitting  a-homoprotocatechuic  acid, 
C6H2(CH3)(OH)2CO2H,  to  dry  distillation.* 

Homocatechol  is  a  syrup  which  readily  dissolves  in  water, 
alcohol,  ether,  and  benzene,  and  can  be  distilled  without 
decomposition.  It  reduces  silver  salts  and  Fehling's  solution 
in  the  cold,  and  gives  a  green  colouration  with  ferric  chloride, 
which  is  converted  into  a  reddish  violet  by  the  addition  of  a 
little  ammonia  or  carbonate  of  soda. 

Homocatechol  monomethyl  ether  or  Creosol,  C6H3(CH3)(OCH3) 
OH(1 : 3 : 4),  occurs  in  beechwood-tar-creosote  and  in  the  pro- 
ducts of  distillation  of  guaiacum  resin.2  In  order  to  prepare 
it,  the  portion  of  creosote  boiling  at  about  220°  is  dissolved  in 
ether  and  treated  with  very  concentrated  alcoholic  potash ;  potas- 
sium creosate,  C8H9K02  -f-  2H2O,  separates  out  in  needles  and  is 
then  decomposed  by  dilute  sulphuric  acid.  It  may  also  be 
prepared  by  heating  a-homovanillic  acid,  C6H3(OH)(OCH3)CH2. 
CO2H,  with  lime  (Tiemann  and  Nagai).  It  is  a  strongly  re- 
fractive liquid  boiling  at  220°,  and  possesses  a  feeble  odour  which 
resembles  that  of  vanilla  and  is  very  pleasant  when  the  vapour 
is  »dilute.  It  produces  a  metallic  mirror  when  warmed  with  a 
solution  of  a  silver  salt,  and  its  alcoholic  solution  is  coloured 
emerald-green  by  ferric  chloride.  Phosphorus  chloride  converts 
it  into  parachlorometacresol  methyl  ether,  C6H3C1(CH3)OCH3, 
(CH3 :  OCH3 :  Cl=l  :  3  : 4),  a  liquid  boiling  at  1850.3 

Homocatechol  dimethyl  ether,  C6H3(CH3)(OCH3)2,  also  occurs  in 
creosote,  and  is  obtained  pure  by  boiling  potassium  creosate  with 
methyl  iodide  and  wood-spirit.  It  is  a  liquid  which  boils  at 
214° — 215°  and  possesses  the  characteristic  smell  of  the  indif- 
ferent oils  which  are  obtained  from  crude  wood-tar.  It  is 
insoluble  in  water  and  alkalis,  and  is  not  coloured  by  ferric 
chloride.4 

2035  Creosote  was  discovered  by  Reichenbach  in  the  year 
1832,  both  in  the  tar  and  the  pyroligneous  acid  obtained  by  the 
distillation  of  beech-wood.5  He  describes  it  as  a  colourless, 
strongly  refractive  liquid,  which  begins  to  boil  at  203°  and 
possesses  an  unpleasant  penetrating  odour,  at  the  same  time 
resembling  that  of  smoked  meat,  and  a  burning  taste.  He 
investigated  its  properties  very  carefully,  and  found  that  it 

1  Tiemann  and  Nagai,  Ber.  Deutsch.  Chem.  Ges.  x.  210. 

2  Hlasiwetz,  Ann.  Chem.  Pharm.  cvi.  339. 

3  Biechele,  ibid.  cli.  115. 

4  Tiemann  and  Mendelsohn,  Ber.  Deutsch.  Chem.  Ges.  viii.  1136. 

8  Schweiger's  N.  Jahrb.  Chem.  Phys.  vi.  301,  345  ;  vii.  1,  57  ;  viii.  57,  399. 


CREOSOTE.  33 


coagulates  albumin,  and  that  fresh  meat  which  has  been  soaked 
in  creosote  for  half  an  hour  to  an  hour  can  be  dried  without 
undergoing  putrefaction.  Such  meat  is  very  tasty,  and 
Reichenbach  therefore  concluded  that  creosote  is  the  antiseptic 
principle  contained  in  smoke.  He  derived  its  name  from  this 
power  of  preserving  meat,  its  most  peculiar  and  most  striking  pro- 
perty, one  too  which  had  been  known  from  the  earliest  times  ;  he 
remarks,  "  The  Greek  word  /cpeas,  meat,  has  a  genitive  /cpeaTos, 
or  Kpea&s,  contracted  to  /cpeo)?  ;  <7<wf&>  signifies  to  preserve,  or 
save;  the  two  may  be  etymologically  united  in  the  word 
creosote,  which  expresses  meat-preserving  or  decay-saving." 

Very  soon  after  this,  Runge  discovered  carbolic  acid,  and 
Laurent  phenyl  hydrate,  in  coal-tar,  the  identity  of  these  bodies 
being  recognised  somewhat  later.  No  clear  views,  however,  were 
held  as  to  the  relation  existing  between  phenol  and  creosote,  and 
a  confusion  arose  which  was  maintained  for  many  years  with  an 
obstinacy  unparalleled  in  the  annals  of  our  science. 

Runge  and  Laurent  showed  that  creosote,  in  spite  of  many 
similarities,  is  quite  a  different  substance  from  the  compound 
obtained  by  them.  Phenol  differs  from  creosote  more  especially 
in  being  an  acid,  in  possessing  a  different  boiling-point,  in 
crystallizing  when  cooled,  and  in  its  different  behaviour  towards 
chlorine,  bromine,  and  nitric  acid.  Runge  moreover  adds  that  it 
imparts  to  meat  preserved  by  it  an  abominable  taste. 

Reichenbach,  nevertheless,  considered  carbolic  acid  to  be 
identical  with  his  creosote,  the  more  so  as  he  thought  that  he 
had  also  discovered  it  in  coal-tar  and  bone-oil. 

Gmelin  was  also  of  this  opinion ;  according  to  him,  carbolic 
acid,  phenyl  hydrate,  and  creosote,  are  chemically  identical,  dif- 
fering only  in  degree  of  purity.  Gmelin's  views  found  universal 
acceptance  ;  crystallized  carbolic  acid  soon  came  into  the  market 
under  the  name  of  creosote  and  displaced  the  genuine  substance 
obtained  from  wood -tar. 

Gorup-Besariez,  who  had  some  of  the  latter  body,  which  had 
been  prepared  by  Reichenbach  at  Blansko,  in  Moravia,  at  his 
disposal,  compared  it  with  "  crystallized  creosote,"  and,  like 
Runge  and  Laurent,  found  them  to  be  completely  different ;  the 
amount  of  substance  in  his  possession,  however,  did  not  admit  of 
a  close  investigation. 

Some  years  later,  Batka  supplied  him  with  fresh  samples  of 
creosote  from  Blansko,  and  he  found  that  when  acted  upon  by 
nitric  acid,  no  picric  acid  was  formed,  while  potassium  chlorate 


34  AROMATIC  COMPOUNDS. 

and  hydrochloric  acid,  instead  of  giving  chloranil,  C6C14O2,  gave 
a  similar  substance,  which,  however,  contained  hydrogen.1 

These  results,  however,  attracted  but  little  attention ;  Gmelin, 
indeed,  mentions  them  in  his  hand-book,  but  only  to  add  that 
Gorup-Besanez,  to  prove  that  creosote  is  a  distinct  substance, 
ought  to  have  prepared  it  himself  instead  of  investigating  a 
commercial  product. 

Two  years  later,  Gorup-Besanez  published  a  more  extended 
treatise  on  creosote  ;  his  determination  of  its  composition  agreed 
with  that  of  Ettling,  who  had  analysed  a  specimen  sent  by 
Reichenbach  to  Liebig. 

By  the  action  of  chlorine  he  obtained  pentachloroxylone, 
C13H7C15O3,  and  hexchloroxylone,  C13H6C16O3,  substances 
which  were  very  similar  to  the  chlorinated  quinones  obtained 
by  Stadeler.2 

About  the  same  period  Yolkel  published  a  paper  on  the 
distillation  products  of  wood,  in  which  he  relates  his  investi- 
gation of  the  creosote  obtained  from  the  tar  in  a  pyroligneous 
acid  works  at  Solothurn.  He  purified  it  by  repeated  solution  in 
caustic  potash,  precipitation  with  sulphuric  acid  and  distillation. 
The  liquid,  after  purification  in  this  manner,  boiled  at  202° — 
208°,  and  in  its  general  properties  resembled  Reichenbach's 
compound,  but  had  a  different  composition,  as  the  following 
results  of  the  analyses  conducted  by  Ettling,  Gorup-Besanez, 
and  Volkel  show :  8 

Creosote  from  Blansko.         Creosote  from  Solothurn. 
(Mean  of  8  Analyses.)  (Mean  of  3  Analyses.) 

Carbon 75 '21  72-45 

Hydrogen 7'90  7'10 

Oxygen 16'89  2045 

100-00  100-00 

Deville  had  previously  analysed  creosote  prepared  by  Pelletier, 
and  obtained  numbers  only  differing  slightly  from  those  of 
Volkel. 

Volkel  considered  that  Gorup-Besanez  had  not  purified  his 
creosote  sufficiently,  whereupon  the  latter  treated  it  repeatedly 
by  Volkel's  method,  without,  however,  altering  the  results 
obtained  by  analysis  to  any  appreciable  extent.4 

In   the  same  year,  Williamson  published  the  results  of  an 

1  Ann.  CJiem.  Pharm.  Ixxviii.  231.  2  Ibid.  Ixxxvi.  233. 

3  Ibid.  Ixxxvi.  66,  93.  4  Ibid.    xcvi.  39. 


HISTORY  OF  CREOSOTE.  35 

investigation  made  by  Fairlie  towards  the  solution  of  the  question 
whether  coal-tar  creosote  consists  chiefly  of  carbolic  acid ;  he 
thus  discovered  the  homologue  of  phenol,  cresyl  hydrate  or 
cresol,  which  boils  at  203°,  or  at  nearly  the  same  temperature 
as  creosote,  thus  introducing  a  new  source  of  confusion.  The 
research  had  no  direct  bearing  on  the  real  issue. 

A  new  chapter  in  the  history  of  creosote  begins  with  Hlasi- 
wetz's  investigation  "  On  Beech- Wood  Tar  Creosote  and  the 
Products  of  Distillation  of  the  Guaiacum  Resin."  He  had 
already  obtained  the  compound  C8H1002  from  the  creosote 
from  Blansko,  and  now  found  it  in  the  distillation  products  of 
guaiacum  resin,  together  with  its  lower  homologue,  guaiacol, 
C7H802,  which  Deville  and  Pelletier  had  already  obtained  from 
the  same  source;  he  therefore  called  his  compound  creosote- 
guaiacol  or  creosol. 

Hlasiwetz  concluded  that  creosote  is  a  kind  of  ether  of  the 
latter,  and  probably  contains  the  radical  C9Hn,  thus  simply 
explaining  the  fact  that  it  contains  more  carbon  than  creosol. 

In  the  following  year  Duclos  published  a  paper  on  cresyl 
alcohol,  which  he  had  not  only  found  in  coal-tar,  but  also  in  the 
tar  from  the  gas-works  at  Giessen  where  only  wood,  and  for  the 
most  part  fir-wood,  was  used.1 

In  criticism  of  this  paper,  Gorup-Besanez  observed  that  these 
results  were  in  opposition  to  all  the  facts  known  concerning 
the  distillation  products  of  wood,  in  which  no  phenols  had  yet 
been  found.  If  Duclos'  results  were  to  be  accepted,  it  would  be 
necessary  to  assume  that  fir-wood  yields  different  products  from 
beech-wood. 

In  the  meantime  Gerhardt  calculated  the  formulae  of  the 
chlorinated  xylones  as  C8H5C13O2  and  C8H4C1402,  according  to 
which  they  appear  to  be  homologues  of  the  chloroquinones,  thus 
confirming  Hlasiwetz's  results ;  Gorup-Besanez  then  undertook 
the  reinvestigation  of  these  compounds,  but  could  not  obtain 
any  creosote  from  Blansko ;  this  source  had  failed. 

In  the  year  1864,  Hugo  Miiller  made  an  important  addition 
to  the  history  of  creosote ;  he  investigated  a  sample  which  had 
been  prepared  in  London  from  Stockholm-tar  and  appeared  to  be 
identical  with  that  from  Blansko.  By  treating  it  with  hydriodic 
acid  be  obtained  methyl  iodide  and  homocatechol  (p.  31). 

These  different  researches  afforded  a  complete  proof  that 
wood-tar  creosote  has  nothing  in  common  with  coal-tar  creosote. 
1  Ann.  Chcm.  Pharm.  cix.  135. 


AROMATIC  COMPOUNDS. 


The  only  obstacles  now  remaining  to  a  complete  concordance  of 
opinion  on  the  subject  were  Reichenbach's  statement,  which  he 
had  never  confirmed,  that  his  creosote  is  contained  in  coal-tar, 
and  that  of  Duclos  that  wood-tar  contains  phenols,  which  no  one 
else  had  been  able  to  detect. 

2036  The  creosote  question  seemed  to  have  received  a  final 
answer,  but  it  was  nevertheless  not  yet  settled.  In  the  year 
1865,  A.  E.  Hofmann  investigated  several  commercial  products 
which  he  obtained  from  various  firms  as  genuine  beech-wood- 
tar  creosote,  and  found  that  they  consisted  chiefly  of  phenol. 
Being  unacquainted  with  the  researches  of  Hlasiwetz  and 
Muller,  he  called  the  existence  of  creosote  in  question  and  con- 
cluded that  it  was  nothing  but  impure  phenyl  hydrate,  the 
chlorinated  xylones  being  mixtures  of  chloranil  with  chlorinated 
phenols.  The  name  of  creosote  ought,  therefore,  to  be  removed 
from  our  list  of  chemical  compounds,  though  this  would  not 
prevent  its  use  as  a  commercial  term. 

Gorup-Besanez  replied  to  this  by  pointing  out  that  Hofmann 
had  only  proved  a  fact  which  had  long  been  known,  that  phenylic 
acid  was  often  sold  under  the  name  of  creosote.  It  was  im- 
possible that  the  firms  mentioned  by  him  could  have  sent 
him  genuine  creosote,  because  this  article  had  long  disappeared 
from  the  German  market.1 

This  incident  had  a  fortunate  conclusion  both  for  Gorup-Besanez 
and  for  tho  facts.  Fresenius  corrected  his  statement,  pointing  out 
that  the  "  Verein  fur  chemische  Industrie  "  at  Mayence  worked 
up  beech-wood-tar  for  creosote.  The  investigation  of  this  showed 
that  it  differed  from  the  Blansko  samples,  but  was  probably 
identical  with  those  from  Solothurn.  Gorup-Besanez  succeeded 
in  extracting  from  it  a  considerable  quantity  of  guaiacol  together 
with  a  smaller  amount  of  creosol ;  by  the  action  of  potassium 
chlorate  and  hydrochloric  acid  on  the  crude  creosote  he  ob- 
tained tetrachloroguaiacone,  C7H2C1402,  and  tetrachlorocreosone, 
C8H4C1402,  homologues  of  chloranil.  When  he  treated  creosote 
with  hydriodic  acid,  he  obtained  methyl  iodide  and  catechol, 
which  were  undoubtedly  derived  from  the  guaiacol.  He  assumed 
that  catechol  is  the  lower  homologue  of  guaiacol  and  creosol, 
both  of  which  yield  chlorine  products  homologous  with  chloranil. 

He  concluded  from  his  analysis  that  Rhenish  creosote  contains 
the  radical  C3H5.2 

1  Journ.  Prakt.  Chem.  xcvii.  63. 

2  Ann.  Chem.  Pharm.  cxliii.  129. 


ORCINOL.  37 


Marasse  opposed  this  view ;  Gorup-Besanez  had  thought  that 
the  fraction  boiling  between  199°  and  208°  is  the  allyl  ether  of 
guaiacol,  the  latter  being  derived  from  it  by  the  action  of  caustic 
potash.  If  this  were  the  case,  allyl  alcohol  or  some  similar  com- 
pound must  be  simultaneously  formed,  whereas  no  one  had 
hitherto  observed  this.  Guaiacol,  he  continues,  may  be  the 
methyl  ether  and  not  the  homologue,  of  catechol,  bearing  the 
same  relation  to  it  as  creosol  to  homocatechol.  The  difference 
between  the  composition  of  creosote  and  that  of  the  two  methyl 
ethers  contained  in  it  is  easily  accounted  for  on  the  supposition 
that  it  contains  substances  which  boil  at  the  same  temperature 
as  guaiacol  and  creosol  but  are  richer  in  carbon  and  poorer  in 
hydrogen. 

He  also  found  that  creosote  contains,  besides  ordinary  phenol, 
its  homologues  cresol  and  phlorol,  which  yield  the  chlorine  pro- 
ducts now  known  as  tetrachlorotoluquinone  and  tetrachloro- 
xyloquinone.1 

The  composition  of  creosote  is  very  variable.  Brauniger 
found  in  one  sample  only  traces  of  phenol  and  less  than  2  per 
cent,  of  cresol,  and  in  that  investigated  by  Gorup-Besanez  only  a 
little  cresol  and  still  less  phlorol,2  while  Tiemann  and  Mendelsohn 
found  large  quantities  of  the  latter.3  The  relative  amounts  of 
guaiacol  and  creosol  are  also  subject  to  great  variations ;  thus 
Biechle  found  scarcely  any  creosol  in  a  second  sample  of  Rhenish 
creosote  obtained  by  Gorup-Besanez.4 

The  higher  boiling  fractions  contain,  moreover,  the  dimethyl 
ethers  of  homocatechol,  pyrogallol,  dimethylpyrogallol,  and 
propylpyrogallol,  which  have  already  been  partially  described. 

The  presence  of  phenols  in  wood-tar-creosote  shows  that  it  is 
more  closely  related  to  the  so-called  coal-tar  creosote  than  was 
previously  supposed.  The  latter  differs  from  the  former  by  the- 
absence  of  guaiacol,  creosol,  and  the  dimethyl  ethers  just  men- 
tioned. These  must  be  derived  from  the  characteristic  aromatic 
compounds  which  various  chemists  have  discovered  in  wood 
(Vol.  III.  Pt.  II.  p.  583). 

ORCINOL,  C6H3(CH3)(OH)2  (1:3:  5). 

2037  Robiquet  discovered  this  compound  in  1829  in  Vario- 
laria  dealbata,  and  named  it  orcin,  because  this  lichen  had 

1  Ann.  Chcm.  Pharm.  clii.  59  2  Ibid,  clxxxv.  339. 

3  Ber.  Deutsch.  Chem.  Ges.  x.  59.  4  Ann.  Chem.  fliarm.  cli.  104. 

234 


38  AROMATIC  COMPOUNDS. 

formerly  been  called  Lichen  orcina,  and  because  the  name  serves 
as  a  reminder  that  the  lichen  is  used  for  the  preparation  of 
archil  (or settle). 1 

Orcinol  was  then  further  investigated  by  various  other  chemists,2 
from  whose  analyses  Gerhardt  first  calculated  its  correct  formula,3 
his  result  being  confirmed  by  the  researches  of  Stenhouse.4 

Orcinol  occurs  in  the  free  state  in  all  the  lichens,  the  various 
species  of  Rocdla,  Lecanora  and  Variolaria,  which  are  em- 
ployed for  the  preparation  of  archil  and  litmus,  and  is  a 
decomposition  product  of  various  acids  and  ether-like  bodies 
prepared  from  these  lichens.  When  these  compounds  are 
heated  with  an  alkali  or  submitted  to  dry  distillation,  orcinol  is 
formed,  e.g : 

Erythrin.  Orsellinic  Acid. 

C7H6(OH)2C02X 

>C4H,(OH),+ 2H,0  =  2C7H5(OH)2C02H 
C7H6(OH)2CO/ 

Erythrol. 

+  C4H6(OH)4. 

Lecanoric  Acid.  Orsellinic  Acid. 

C7H5(OH)O.C02H 

+  H20  =  2C7H5(OH)2C02H. 
C7H5(OH)2CO 

Orsellinic  Acid.  Orcinol. 

C7H5(OH)2C02H  =  C7H6(OH)2  +  CO2. 

In  order  to  prepare  orcinol,  6  parts  of  Rocella  fuciformis  are 
-macerated  for  twenty  minutes  with  60  parts  of  milk  of  lime  con- 
taining 1  part  of  lime,  the  mass  filtered  and  the  erythrin  pre- 
cipitated from  the  filtrate  by  hydrochloric  acid ;  this  is  boiled 
for  half  an  hour  with  a  slight  excess  of  milk  of  lime,  the  solu- 
tion filtered,  treated  with  carbon  dioxide  to  remove  the  excess  of 
lime,  and  evaporated  nearly  to  dryness.  The  orcinol  is  extracted 
from  the  residue  by  benzene,  while  erythrol  is  left  behind.  When 
the  benzene  solution  is  shaken  with  water,  the  orcinol  is  taken  up 
by  the  latter  and  is  obtained  pure  on  evaporation.5  The  crude 

1  Ann.  Chim.  Phys.  xlii.  236. 

2  Dumas,  Ann.   Chem.   Pharm.    xxvii.    140  ;   Liebig  and  "Will,  ibid,   xxvii. 
147  ;  Sclmnk,  ibid.  xli.  159  ;  liv.  269. 

3  Compt.  Rend.  Chim.  1845,  287. 

4  Phil.  Trans.  1848,  63  ;  1349,  393. 

5  Stenhouse. 


ORCINOL.  .      39 


orcinol  can  also  be  purified  by  distillation,1  which  is  best  carried 
on  in  vacuo.2 

Vogt  and  Henninger  first  prepared  orcinol  from  toluene,  by 
chlorinating  toluene  in  presence  of  iodine,  and  warming  the 
chlorotoluene  with  two  to  three  times  its  weight  of  sulphuric 
acid  on  the  water-bath  ;  two  sulphonic  acids  are  thus  formed, 
which  readily  admit  of  separation,  the  barium  salt  of  the  one 
being  much  more  soluble  than  that  of  the  other,  whith  yields 
orcinol  when  fused  with  caustic  potash.3 

The  chlorotoluene  obtained  by  the  method  described  is  a 
mixture  of  parachlorotoluene  with  a  little  orthochlorotoluene ; 
since,  however,  the  side  chains  of  orcinol  are  arranged  symmetri- 
cally, an  inter-molecular  change  must  take  place  during  its 
preparation  just  as  in  that  of  resorcinol  from  benzeneparadi- 
sulphonic  acid. 

Neville  and  Winther  obtained  orcinol  by  fusing  symmetric 
bromotoluenesulphonic  acid,  the  toluenemetadisulphonic  acid 
obtained  from  orthotoluidinedisulphonic  acid,  or  bromometa- 
cresol  with  caustic  potash ;  they  also  prepared  it  by  heating 
metadibromotoluene  to  280° — 300°  with  caustic  potash  and  a 
little  water,  and  finally  by  replacing  the  amido-group  of  amido- 
metacresol  by  hydroxyl.4 

Orcinol  is  also  formed,  together  with  parahydroxybenzoic  acid, 
when  aloes  are  fused  with  caustic  soda.5 

Properties. — Orcinol  is  readily  soluble  in  water,  alcohol,  and  ether, 
and  crystallizes  with  one  molecule  of  water  in  six-sided  monoclinic 
prisms,  which  effloresce  gradually  over  sulphuric  acid,  and  more 
rapidly  when  heated  to  100°.  It  is  almost  completely  precipi- 
tated in  fine  needles  when  its  concentrated  solution  is  warmed 
with  a  saturated  solution  of  common  salt  (Lamparter) ;  it  reduces 
ammoniacal  silver  solution,  has  an  intensely  sweet  but  unpleasant 
taste,  and  melts  in  the  anhydrous  state  at  106'5° — 108°  (Neville 
and  Winther).  When  rapidly  heated,  it  distils  almost  without 
decomposition  between  287°  and  290°  (Dumas).  Ferric  chloride 
produces  a  violet-black  colouration,  and  bleaching  powder  a  dark 
red,  soon  changing  to  yellow.  In  the  presence  of  ammonia  and 
air  it  is  converted  into  orcein,  the  colouring  matter  of  archil, 
and  becomes  coloured  a  deep  reddish  violet  (Robiquet).  Its 

Lamparter,  ibid,  cxxxiv.  215. 

De  Luynes,  Ann.  Chim.  Phys.  [4]  vi.  184. 

Ann.  Chem.  Pharm.  clxv.  366  ;  Bull.  Soc.  Chim.  xxi.  373. 

Ber.  Deutsch.  Chem.  Gcs.  xv.  2976. 

Barth  and  Hlasiwetz,  Ann.  Chem.  Pharm.  cxxxiv.  288. 


40  AROMATIC  COMPOUNDS. 

alkaline  solution  when  heated  with  a  little  chloroform  becomes 
coloured  first  purple-red  and  then  bright  red,  and  on  dilution 
with  water  has  an  intense  greenish  yellow  fluorescence,  homo- 
fluorescein,  C23H18O5,  being  formed.  This  reaction  is  so  delicate 
that  the  compounds  which  yield  orcinol  can  readily  be  detected 
in  the  lichens  by  its  means.  A  few  pieces  are  boiled  with  5  per 
cent,  caustic  potash  and  a  little  chloroform  added  to  the  clear 
solution  ;  it  is  then  warmed  for  ten  minutes  on  the  water-bath 
and  diluted.1 

Orcinol  may  be  quantitatively  determined  by  adding  standardized 
bromine  water  to  the  dilute  solution  until  tribromorcinol  is  no 
longer  precipitated  and  determining  the  excess  of  bromine  by  a 
solution  of  potassium  iodide.2 

Orcinol  monomethyl  ether,  C6H3(CH3)(OCH3)OH,  is  formed, 
together  with  the  dimethyl  ether,  when  orcinol  is  boiled  with 
caustic  potash,  methyl  iodide,  and  wood-spirit.  It  is  a  light 
yellow,  oily  liquid  which  boils  at  273°  and  is  soluble  in  alkalis. 

Orcinol  dimethyl  ether,  C6H3(CH3)(OCH3)2,  is  a  yellowish, 
mobile  fluid  which  boils  at  244°,  is  insoluble  in  alkalis,  and  is 
converted  by  oxidation  into  symmetric  dimethoxybenzoic  acid, 
or  dimethyl— a— resorcylic  acid,  C6H3(OCH3)2C02H(5  :  3 : 1),  thus 
establishing  the  constitution  of  orcinol.3 

Orcinol  acetate,  C6H3(CH3)(OC2H3O)2,is  obtained  by  the  action 
of  acetyl  chloride  on  orcinol,  and  crystallizes  from  alcohol  in 
needles  melting  at  25°.* 

Orcinol  dicthylcarbonate,  C6H3(CH3)(O.COOC2H5)2,  is  obtained 
by  the  action  of  chlorocarbonic  ether  on  the  potassium  compound 
of  orcinol,  and  is  a  thick,  oily  liquid  boiling  at  310° — 3120.5 

Orcinolazolenzene,  C6H5N=NC6H2(CH3)(OH)2,  is  formed  when 
orcinol  and  diazobenzene  nitrate  are  brought  together  in  aqueous 
solution.  It  crystallizes  from  a  mixture  of  acetic  acid  and  acetic 
ether  in  dark  red  needles  melting  at  1830.6 

1  Schwarz,  Ber.  Dcutsch.  Chem.  Ges.  xiii.  543. 

2  Reymann,  ibid.  viii.  790. 

3  Streng  and  Tiemann,  ibid.  xiv.  1999. 

4  Luynes  and  Lionet,  Zeitschr.  Chcm.  1867,  561. 

5  Wallach,  Licbig's  Ann.  ccxxvi.  86. 

6  Typke,  Ber.  Deutsch.  Chcm.  Ges.  x.  1579. 


SUBSTITUTION  PRODUCTS  OF  ORCINOL.  41 


SUBSTITUTION    PRODUCTS   OF  ORCINOL. 

2038  These  are  obtained  by  the  same  methods  as  the  cor- 
responding resorcinol  compounds,  which  they  resemble  very 
closely. 

CHLORINE  SUBSTITUTION  PRODUCTS. 

Melting- 
point. 

Trichlororcinol,1       C6C13(CH3)(OH)2,       long  needles     123° 
Pentachlororcinol,2  C6C13(CH3)(OC1)2,      large  prisms      120°'5 

BROMINE  SUBSTITUTION  PRODUCTS. 

Monobromorcinol,3  C6H2Br(CH3)(OH)2,   crystals  135° 

Dibromorcinol,4        C6HBr2(CH3)(OH)2,  needles  '    146° 

Tribromorcinol,5       C6Br3(CH3)(OH)2,      needles  98° 

Pentabromorcinol,6  C6Br3(CH3)(OBr)2,     triclinic  crystals  126° 

IODINE  SUBSTITUTION  PRODUCTS. 

Mono-iodorcinol,7     C6H2I(CH3)(OH)2,     prisms  80°'5 

Tri-iodorcinol,8         C6I3(CH3)(OH)2,   brown  tablets 

NlTRO-SUBSTITUTION  PRODUCTS. 

(  golden  ) 

-Nitro-orcinol,9     C6H2NO2(CH3) (OH)2,  ^  lustrous  V     120° 

(needles  ) 
(    dark    \ 

-Nitro-orcinol,     C6H2NO2(CH3)(OH)2J  yellow          115° 

(needles  J 
f    deep    ^ 

-Dinitro-orcinol,10C6H(NO2)2CH3(OH)2,^  yellow          164°'5 

(  tablets  J 

1  Stenhouse,  Proc.  Roy.  Soc.  1871. 

2  Stenhouse,  Dittler  and  Liebermann,  Ann.  Chem.  Pharm.  clxix.  265. 

3  Lamparter,  loc.  cit.  4  Tiemann  and  Streng,  loc.  cit. 
Stenhouse  and  Groves,  Journ.  Chem.  Soc.  1880,  402. 

6  Stenhouse  and  Rammelsberg  ;  Dittler  and  Liebermann,  loc.  cit.  255. 

7  Stenhouse,  Proc.  Roy.  Soc.  xxii.  53. 

8  Stenhouse,  Journ.  Chem.  Soc.  1864,  327. 

9  Weselsky,  Ber.  Deutsch.  Chem.  Ges.  vii.  441. 

10  Stenhouse  and  Groves,  Journ.  Chem.  Soc.  1877,  i.  548. 


AROMATIC  COMPOUNDS. 


(  golden 
i>\ 


Melting- 
point. 


^-Dinitro-orcmol,1C6H(NO2)2CH3(OH)2,-|  yellow    V  109°— 110° 

(needles  J 
C    long    ^ 

Trinitro-orcinol,2     C6(NO2)3CH3(OH)2,     ]  yellow          163'5° 

(needles  J 

2039  Archil.  This  name  was  formerly  employed  to  designate 
both  the  colouring  matter  which  is  extracted  from  the  lichens 
just  mentioned,  and  the  lichens  themselves.  Theophrastos  and 
Dioscorides  mention  a  plant  (f>vicos  6a\daaiov  or  TTOVTIOV,  called 
by  Pliny  Fucus  marinus,  which  is  not  a  sea-weed,  as  the  name 
might  be  taken  to  imply,  but  a  lichen  which  grows  on  the  rocks 
of  certain  islands,  especially  Crete,  and  is  capable  of  dyeing  wool 
a  beautiful  violet  or  purple  colour. 

Archil  came  into  the  European  market  as  early  as  the  four- 
teenth century;  the  following  account  of  it  is  given  by  Beck- 
mann  :8 

Among  the  oldest  and  principal  Florentine  families  is  that 
known  under  the  name  of  Oricellarii  or  Rucellarii,  Ruscellai  or 
Rucellai,  several  of  whom  have  distinguished  themselves  as 
statesmen  and  men  of  letters.  This  family  are  descended  from 
a  German  nobleman  named  Ferro  or  Frederigo,  who  lived  in  the 
beginning  of  the  twelfth  century.  One  of  his  descendants  in 
the  year  1300  carried  on  a  great  trade  in  the  Levant,  by  which 
he  acquired  considerable  riches,  and  returning  at  length  to 
Florence  with  his  fortune,  first  made  known  in  Europe  the  art 
of  dyeing  with  archil.  It  is  said  that  a  little  before  his  return 
from  the  Levant,  happening  to  make  water  on  a  rock  covered 
with  this  lichen,  he  observed  that  the  plant,  which  was  then 
called  respio  or  respo,  and  in  Spain  orciglia,  acquired  by  the 
urine  a  purple,  or,  as  others  say,  a"  red  colour.  He  therefore 
tried  several  experiments,  and  when  he  had  brought  to  perfection 
the  art  of  dyeing  wool  with  this  plant,  he  made  it  known  at 
Florence,  where  he  alone  practised  it  for  a  considerable  time  to 
the  great  benefit  of  the  state.  From  this  useful  invention  the 
family  received  the  name  Oricellarii,  from  which  at  last  was 
formed  Rucellai. 

1  Leeds,  Ber.  Deuisch.  Chem.  Ges.  xiv.  483. 

2  Stenhouse,  Proc.  Hoy.  Soc.  xix.  41  ;  Merz  and  Zeller,  Ber.  Deutsch.   Chem. 
Ges.  xii.  2038. 

3  Beckmann's  History  of  Inventions,  vol.  i.  p.  37. 


ARCHIL.  43 


As  several  documents,  still  preserved  among  the  Florentine 
archives,  confirm  the  above  account  of  the  origin  of  this  family 
name,  from  the  discovery  of  dyeing  with  oricello,1  we  may,  in 
my  opinion,  consider  it  as  certain  that  the  Europeans,  and  first 
the  Florentines,  were  made  acquainted  with  this  dye-stuff  and 
its  use  in  the  beginning  of  the  fourteenth  century.  At  that 
time  the  Italians  brought  from  the  East  the  seeds  of  many  arts 
and  sciences,  which,  afterwards  sown  and  nurtured  in  Europe, 
produced  the  richest  harvests ;  and  nothing  is  more  certain  than 
that  the  art  of  dyeing  was  brought  to  us  from  the  East  by  the 
Italians.  I  do  not  believe  that  the  merit  of  having  discovered 
this  dye  by  the  above-mentioned  accident  is  due  to  that  Floren- 
tine ;  but  I  am  of  opinion  that  he  learned  the  art  in  the  Levant, 
and  on  his  return  taught  it  to  his  countrymen,  which  was  doing 
them  no  small  service. 

The  archil  lichens,  the  most  valuable  of  which  are  Eocella  tine- 
toria  and  It.  fuciformis,  occur  in  several  varieties  and  in  con- 
siderable quantity  on  the  coasts  of  warm  and  tropical  countries, 
such  as  the  islands  of  the  Mediterranean,  the  Canary  and  Cape 
Verde  Islands,  Madagascar,  Zanzibar,  Angola,  Ceylon,  Java, 
Peru,  Chili,  &c. 

The  old  method  for  the  preparation  of  archil  consisted  in 
treating  the  lichens  with  stale  urine  and  lime  in  large  casks 
provided  with  moveable  lids,  a  considerable  quantity  of  alum 
and  white  arsenic  being  added  to  prevent  the  fermentation  from 
passing  to  a  further  stage.  The  mixture  is  well  agitated  for  a 
month  and  then  stored  in  casks  in  which  it  is  allowed  to  stand 
for  a  long  time  before  use,  the  colour  being  found  to  improve  on 
ceeping. 

A  more  modern  process  consists  in  treating  the  finely-chopped 
ichens  with  dilute  ammonia,  and  keeping  the  mixture  at  the 
jmperature  of  the  air  or  at  a  slightly  higher  one  until  a  dark 
dolet  paste  has  been  formed ;  this  is  diluted  with  ammonia  and 
iltered  through  a  press ;  the  solution  thus  obtained  is  known  as 
)lue  archil.  Red  archil  is  obtained  from  this  by  gentle  heating, 
ammonia  being  thus  removed. 

Stenhouse  proposed  first  to  extract  the  lichens  with  milk 
)f  lime,  precipitate  the  solution  with  hydrochloric  acid  and 
rork  up  the  erythrin,  &c.,  thus  obtained  as  by-products,  the 

1  These   documents  from  the  Florentine  records  may  be  found  in  Dominici 
fariae  Manni  de  Florentinis  Inventis  Commentarium.     Ferrariae  1731.     Beck- 
inn  quotes  the  passage  in  question. 


44  AROMATIC  COMPOUNDS. 

colouring  matter  being  thus  left  in  a  much  purer  condition. 
Marnas  of  Lyons  found  that  the  best  results  were  obtained  by 
extracting  with  dilute  ammonia  and  warming  the  compounds 
precipitated  from  the  solution  with  ammonia  in  a  current  of  air 
to  70°  for  about  three  weeks.  On  addition  of  calcium  chloride 
a  precipitate,  known  as  French  purple  (ponrpre  franpaise),  is 
thrown  down,  and  the  material  thus  obtained  yields  much  finer 
and  clearer  shades  than  archil. 

Since  the  discovery  of  the  aniline  dyes,  archil  has  lost  much 
of  its  commercial  importance  ;  it  is  now  only  used  in  combina- 
tion with  other  colouring  matters  in  order  to  obtain  certain 
shades  of  brown,  and  for  the  production  of  a  cheap  blue  for  wool 
dyeing ;  the  material  is  first  grounded  with  indigo  and  then  dyed 
with  archil,  the  result  being  a  dye  which  is  similar  to  that  of 
genuine  indigo-blue. 

Cudbear  or  Persia.  The  inhabitants  of  Sweden,  Scotland, 
Ireland,  Wales,  &c.,  have  for  centuries  been  in  the  habit  of 
using  various  kinds  of  lichen,  especially  Lecanora  tinctoria,  for 
wool-dyeing,  the  colour  being  produced  by  treatment  of  the 
lichen  with  urine.  During  last  century  a  patent  was  taken  out 
by  Dr.  Cuthbert  Gordon  for  the  preparation  of  cudbear,1  by 
drying  and  powdering  the  pasty  mass  obtained  by  the  action  of 
ammonia  or  urine  on  the  lichens.  Cudbear  is  prepared  in  the 
Auvergne  from  Variolaria  orcina  by  a  similar  method. 

Orceln.  Robiquet  has  given  this  name  to  the  colouring 
matter  of  archil,  which  is  formed,  as  he  discovered,  by  the  action 
of  hydrogen  and  ammonia  on  orcinol.2  Gerhardt  calculated  its 
formula  from  the  analyses  of  Dumas  and  Kane,3  and  gave  the 
following  equation  for  its  formation  : 

C7H802  +  NH3  +  30  =  C7H7N03  +  2H2O. 

Kane  prepared  orcein  from  commercial  archil ;  he  describes  it 
as  a  carmine-red  powder,  containing  carbon  and  nitrogen  in  a 
constant  ratio,  while  the  amount  of  oxygen  is  variable,  being 
larger  as  the  archil  becomes  older ;  hence  he  assumed  that  it 
consists  of  two  similar  colouring-matters,  a-orcein  and  /3-orcein. 

Liebermann,  who  obtained  the  colouring  matter  by  the  action 
of  gaseous  ammonia  and  air  on  pure  orcinol,  found  that  two 

1  Bancroft,  Philosophy  of  Permanent  Colours,  1813,  i.  300. 

2  Ann.  Chim.  Phys.  Iviii.  320. 

8  Ann.  Chem.  Pharm.  xxxix.  25. 


CUDBEAR  AND  LITMUS.  45 

compounds     are    thus     formed     according    to     the     following 
equations : 

2C7H802 + NH3  +  30  =  C14HnN08  +  3H20 

CUH13N04  +  NH3  +  0  =  C14H12N203  +  2H2O. 

The  latter  is  therefore  formed  in  larger  quantity  when  the 
a,ction  of  the  ammonia  is  allowed  to  continue  for  some  time ;  it 
is  less  soluble  in  aqueous  ammonia  and  alcohol  than  the  former 
compound.  Both  occur  as  amorphous  masses  having  a  beetle- 
green  lustre,  and  forming  splendid  purple  solutions  with  alkalis ; 
but  the  solution  of  the  second  compound  has  a  bluer  shade  than 
that  of  the  first.1 

2040  Litmus  (tournesolso  Zac&mws)  was  discovered  by  the  Dutch.2 
It  is  prepared  from  various  species  of  Rocella,  Variolaria  and 
Lecanora,  by  allowing  them  to  ferment  in  contact  with  ammonia 
and  carbonate  of  potash,  as  in  the  manufacture  of  archil.  When 
the  mass  has  become  violet,  stale  urine,  lime  and  potashes  are 
added,  and  the  mass  again  allowed  to  ferment  until  it  has  as- 
sumed a  blue  colour ;  it  is  then  mixed  with  gypsum  or  chalk, 
and  a  little  indigo,3  and  made  up  into  small  tablets. 

Kane  was  the  first  more  accurately  to  investigate  litmus,  and  he 
obtained  several  colouring  matters  and  other  substances  from  it.4 
Wartha,  who  also  investigated  the  colouring  matter  of  litmus, 
found  indigo  in  it ;  this,  however,  had  probably  been  purposely 
added  as  just  described,  although  it  may  possibly  have  been 
derived  from  the  urine,  which  is  known  to  contain  appreciable 
quantities  of  a  substance  which  yields  indigo  on  decomposition. 
On  extracting  litmus  with  cold  alcohol,  Wartha  obtained  a  red 
colouring  matter  which  is  indifferent  towards  acids,  and  yields 
litmus  blue  and  another  substance  when  treated  with  water. 
On  evaporating  the  solution  and  treating  the  residue  with 
absolute  alcohol  and  a  little  acetic  acid,  a  scarlet  colouring 
matter  is  removed,  and  this  is  changed  to  a  purple  by  ammonia, 
while  the  pure  litmus  blue  remains  behind  as  a  brown  powder, 
which  forms  a  reddish  brown  aqueous  solution  turned  blue  by 
the  slightest  trace  of  an  alkali.5 

According  to  De  Luynes,  the  pure  colouring  matter  is  obtained 
by  digesting  1  part  of  orcinol  with  5  parts  of  ammonia  and  25 

1  Bcr.  Deutsch.  diem.  Ges.  viii.  1649. 

2  The  origin  of  this  name  is  unknown  ;  it  may  perhaps  be  derived  from  Lacca 
musci,  a  lake  prepared  from  moss.  3  Gottlieb,  Chcm.  Tech.  p.  531. 

4  Loc.  cit.  5  Ber.  Deutsch.  Ghent.  Ges.  ix.  217. 


46  AROMATIC  COMPOUNDS. 

parts  of  crystallized  carbonate  of  soda  for  four  or  five  days  at 
60°— 80°,  and  precipitating  the  solution  with  hydrochloric  acid.  It 
is  only  slightly  soluble  in  water,  and  the  wine-red  colour  of  this 
solution  is  changed  to  bluish  violet  by  alkalis,  and  to  a  reddish 
brown  by  acids.  It  yields  a  red  solution  with  alcohol,  and  a 
yellow  one  with  ether.  De  Luynes  considers  that  the  colouring 
matter  is  a  weak  acid  which  forms  blue  salts,  the  potassium 
salt  existing  in  litmus.1 

Litmus  is  not  only  employed  in  the  laboratory  in  the  form  of 
litmus  paper  and  tincture,  but  is  also  used  for  colouring  wine 
and  vinegar.  The  colouring  matter  can  readily  be  recognized  by 
its  absorption  spectrum ;  ether  extracts  it  from  an  acid  solution 
yielding  a  yellow  liquid  which  absorbs  the  left  end  of  the  spec- 
trum up  to  E  \  D.  A  drop  of  ammonia  colours  the  solution 
blue,  an  absorption  band  being  formed  which  begins  at  d,  where 
it  is  very  intense,  gradually  diminishing  to  E.  On  shaking  with 
water  the  colouring  matter  is  taken  up,  and  the  blue  solution 
gives  an  absorption  band  at  D  ;  the  addition  of  acid  now  changes 
the  colour  to  brick-red,  and  the  solution  gives  an  absorption 
spectrum  similar  to  that  of  wine.2 

Ribbon  Litmus  (Tournesollappen,  tournesol  en  drapeaux,  Bezetta, 
Lackmus  in  Fleckchen)  is  obtained  in  southern  France  from 
the  expressed  sap  of  Croton  tinctorium ;  linen  rags  are  soaked 
in  the  sap,  dried  in  the  sun,  and  then  exposed  on  heaps  of 
horse-dung  covered  with  chopped  straw,  the  ammonia  evolved 
being  sufficient  to  change  the  colour  of  the  rags,  which  are  fre- 
quently turned,  to  blue.  They  are  then  again  dipped  in  the 
sap,  to  which  urine  has  been  added,  the  colour  thus  produced 
becoming  dark  green  or  purple-red  on  drying,  and  they  are  then 
brought  into  the  market.  It  was  formerly  believed  that  the 
Dutch  employed  them  for  the  manufacture  of  litmus,  but  this  is 
not  the  case ;  they  are  actually  used  to  colour  the  exterior  of 
cheeses  red. 

The  colouring  matter  contained  in  these  ribbons  has  not  been 
accurately  investigated;  acids  change  it  to  red,  but  the  blue 
colour  is  not  restored  by  alkalis. 

1  Jahresber.  1864,  551. 

2  Vogel,  Spectralanalyse,  p.  269. 


CRESORCINOL.  47 


CRESORCINOL,  C6H3(CH3)(OH)2(1 : 2  : 4). 

2041  This  dihydroxy toluene,  which  was  called  lute-rein  by 
Vogt  and  Henninger,  may  be  prepared  from  ft-  and  7-amido- 
paracresol  by  the  diazo-reaction l  and  by  fusing  bromoparacresol 
with  caustic  potash.2 

It  is  readily  soluble  in  water,  alcohol,  ether  and  benzene,  and 
crystallizes  in  monosymmetric  prisms  which  form  characteristic 
spherical  aggregates  and  melt  at  104°  — 105°.  Ferric  chloride 
produces  an  unstable,  greenish  blue  colouration,  and  an  alkaline 
solution  becomes  coloured  red  in  the  air.  Like  resorcinol  it  re- 
duces silver  solution  in  the  cold,  is  not  precipitated  by  lead 
acetate,  and  gives  a  precipitate  with  bromine  water  which  soon 
becomes  crystalline.  On  heating  with  phthalic  anhydride  and 
dissolving  the  mass  in  dilute  caustic  soda,  a  solution  is  formed 
possessing  as  fine  a  green  fluorescence  as  does  that  obtained  by 
a  similar  process  from  resorcinol.  It  differs  however  from  the 
latter  in  yielding  no  colouring  matter*  when  heated  with  sul- 
phuric acid  and  nitrobenzene.  In  presence  of  ammonia  and 
moist  air  it  is  converted  into  yellow  cresorcein,  which  dissolves 
in  dilute  caustic  soda,  forming  a  blue  solution  turned  red  by 
acetic  acid. 

Isorcinol.  Senhofer  obtained  this  compound  by  the  fusion  of 
7-toluenedisulphonic  acid,3  and  Hakansson  prepared  a-isorcinol 
in  a  similar  manner  from  a-toluenedisulphonic  acid.4  Claesson 
subsequently  showed  that  these  two  sulphonic  acids  are  identical, 
and  that,  therefore,  only  one  isorcinol  can  exist.  It  crystallizes 
*n  needles  melting  at  87°— 88°,  but  it  resembles  cresorcinol 
so  closely  that  Neville  and  Winther  look  upon  the  two  as 
identical,  an  opinion  which  is  supported  by  the  fact  that  the 
toluenedisulphonic  acid  has  the  side  chains  in  the  same  relation 
as  cresorciaol. 

1  Knecht,  Ber.  Deutsch.  Chem.  Gcs.  xv.  298  and  1069  ;  Ann.  Chem.  Pharm. 
ccxv.  83  ;  Wallach,  ibid.  xv.  2831  ;  Neville  and  Winther,  ibid.  xv.  2980. 

2  Vogt  and  Henninger,  ibid.  xv.  1081. 

3  Ann.  Chem.  Pharm.  clxiv.  131. 

4  Ber.  Deutsch.  Chem.  Ges.  v.  1084. 


48  AROMATIC  COMPOUNDS. 


TOLUQUINOL,  OR  TOLUHYDROQUINONE. 
C6H3(CH3)(OH)2(1:2:5). 

2042  This  compound  may  be  obtained  from  orthotoluidine 
just  as  is  quinol  from  aniline,1  and  may  also  be  prepared  from 
/3-amido-orthocresol  by  means  of  the  diazo-reaction.2  It  is 
readily  soluble  in  water,  alcohol  and  ether,  and  crystallizes  from 
hot  benzene  or  toluene  in  pointed,  rhombic  plates  which  have  a 
nacreous  lustre  and  melt  at  124°.  Caustic  soda  produces  a 
bluish  green  colouration  which  rapidly  changes  to  dark  brown ; 
bleaching  powder  solution  gives  the  same  reaction,  but  when 
very  dilute  produces  a  brownish  red  colour.  Oxidizing  agents 
readily  convert  it  into  toluquinone. 

Toluquinol  monomethyl  ether,  C6H3(CH3)(OCH3)OH,  is  formed, 
together  with  the  compound  described  below,  by  heating  tolu- 
quinol  with  caustic  soda,  methyl  iodide  and  wood-spirit  to  190°. 
It  has  a  faint  smell  of  creosote,  crystallizes  in  plates  melting  at 
72°,  boils  at  240°  — 245°,  and  yields  toluquinone  on  oxidation. 

Toluquinol  dimethyl  ether,  C6H3(CH3)(OCH3)2,  can  easily  be 
separated  from  the  monomethyl  ether,  since  it  is  insoluble  in 
alkalis  and  non-volatile  in  steam.  It  is  a  liquid  which  has  a 
pleasant  smell  like  fennel  and  boils  at  214°  — 218°.  When 
oxidized  by  chromic  acid  in  acetic  acid  solution,  it  is  converted 
into  a  compound,  C16H1604,  which  is  precipitated  by  water  in 
brick-red  needles  and  crystallizes  from  its  deep  yellow  alcoholic 
solution,  in  hair-like  needles,  which  appear  almost  black  when 
seen  in  masses  and  become  silver-grey  on  drying.  They  melt  at 
153°  and  sublime  when  more  strongly  heated.  Ammonium  sul- 
phide reduces  it  to  the  compound  C18H18O4,  crystallizing  from 
alcohol  in  small  prisms,  melting  at  173°,  which  are  readily 
re-oxidized. 

Diacetotoluquinol,  C6H3(CH3)(OCO.CH3)2,  is  formed  by  the 
action  of  acetyl  chloride  on  toluquinol ;  it  crystallizes  from 
alcohol  in  large  tablets  melting  at  72°  (Nietzki). 

1  Nietzki,  Ber.  Deutsch.  Chem.  Gcs.  x.  834,   1935  ;  Ann.  Chem.  Pharm.  ccxv. 
158. 

2  Neville  and  Winther,  Ber.  Deutsch.  Chem.  Gcs.  xv.  2979. 


TOLUQUINOL  AND  TOLUQUINONE.  49 


TOLUQUINONE,   C6H3(CH3)02. 

2043  This  compound  is  formed  when  paradiamidotoluene,1 
crude  cresol2  or  amidorthocresol 3  is  oxidized  with  manganese 
dioxide  and  dilute  sulphuric  acid,  or  when  orthotoluidine  hydro- 
chloride  is  heated  with  ferric  chloride.4  It  crystallizes  in  small 
golden-yellow  plates  which  readily  volatilize,  have  a  penetrating 
smell  resembling  that  of  benzoquinone,  and  melt  at  69°.  It 
dissolves  slightly  in  cold,  more  readily  in  hot  water,  forming  a 
golden-yellow  solution  which  is  coloured  brownish  red  by  alkalis. 
Sulphurous  acid  reduces  it  to  toluquinol. 

Dianilidotoluquinone,  C6H(CH3)02(NH.C6H5)2,  is  obtained  by 
the  action  of  aniline  on  toluquinone  in  alcoholic  solution; 
it  crystallizes  from  hot  glacial  acetic  acid  in  brown,  matted 
needles,  which  melt  at  232°  — 233°  and  form  a  blood -red  solution 
in  sulphuric  acid.  When  boiled  with  alcohol  and  sulphuric 
acid,  anilidoliydroxy toluquinone,  C6H(CH3)02(NH.C6H5)OH,  is 
formed ;  it  crystallizes  from  alcohol  or  acetic  acid  in  deep  blue 
needles  and  forms  salts  with  bases. 

Dianilidotoluquinone  anilide,  C6H(CH3)0(NC6H5)(NH.C6H5)2, 
is  formed  when  aniline  and  toluquinone  are  brought  together  in 
solution  in  a  mixture  of  alcohol  and  acetic  acid.  It  crystallizes 
in  broad  dark-brown  plates  which  have  a  blue  surface  lustre, 
melt  at  167°  and  combine  with  acids  to  form  salts,  which  are  only 
slightly  soluble  in  water  but  crystallize  well  from  alcohol. 

On  heating  with  alcoholic  sulphuric  acid,  anilido-ethoxytolu- 
quinone  anilide,  C6H(CH3)0(NC6H5)(NH.C6H5)OC2H5,is  formed ; 
this  compound  crystallizes  from  alcohol  in  silky,  red  needles 
melting  at  115° — 116°,  is  a  tolerably  strong  base  and  forms  blue 
salts.  It  dissolves  in  concentrated  sulphuric  acid  with  a  green 
colour.  On  treatment  with  alcoholic  potash  it  yields  anilido- 
hydroxytoluquinone  anilide,  C6H(CH3)0(NC6H5)(NHC6H5)OH, 
crystallizing  from  hot,  dilute  acetic  acid  in  brownish  needles, 
which  form  a  deep  green  solution  in  sulphuric  acid.  It  forms 
insoluble  or  difficultly  soluble  salts  with  the  metals. 

Dihydroxy toluquinone,   C6H(CH3)02(OHJ2,    is  obtained    from 

1  Nietzki,  loc.  cit. 

2  Carstanjen,  Journ.  Prakt.  Chem.  [2]  xxiii.  425. 

3  Nolting  and  Kohn,  Bcr.  Deutsch.  Chem.  Ges.  xvii.  370. 

4  Ladenburg,  ibid.  x.  1125. 


50  AROMATIC  COMPOUNDS. 

the  preceding  compound  by  the  action  of  very  dilute  caustic  potash 
solution.  It  is  readily  soluble  in  most  solvents  and  crystallizes 
from  them  badly ;  it  readily  sublimes,  however,  in  brownish 
yellow,  lustrous  plates,  melting  at  177°.  Its  salts  form  insoluble 
or  only  slightly  soluble  precipitates  which  are  not  characteristic.1 
Toluquinhydrone,  C(.H3(CH3)O2-hC6H3(CH3)(OH)2,  is  obtained 
by  mixing  aqueous  solutions  of  the  two  constituents,  and  crys- 
tallizes in  fine,  almost  black  needles  which  melt  at  52°  and  are 
tolerably  soluble  in  water  forming  a  brownish  yellow  solution 
(Nietzki). 


SUBSTITUTION  PRODUCTS  OF  TOLUQUINONE. 

The  chlorine  substitution  products  are  obtained  by  treating 
orthocresol  or  metacresol,  and  therefore  also  crude  cresol,  with 
potassium  chlorate  and  hydrochloric  acid.2  Trichloroquinone  is 
likewise  formed  by  this  method  from  orthotoluidineparasulphonic 
acid.3  Sulphurous  acid  converts  them  into  the  corresponding 
derivatives  of  toluquinol. 

Dichlorotoluquinone,      C7H4C12O2,     yellow  transparent  tablets. 
Trichlorotoluquinone,      C7H3C13O2,     yellow  plates. 

Tetrachlorotoluquinone,C7H2Cl402,      { ^^ 
Tribromotoluquinone,4    C7H3Br3O2,     yellow  plates. 


TOLUQUINONOXIME  COMPOUNDS. 

2044  a-Toluquinonoxime,  C6H3(CH3)0(NOH).  This  compound, 
which  is  generally  known  as  nitroso-orthocresol,  is  formed  in  an 
analogous  manner  to  quinonoxime  (Part  III.  p.  171)  by  the  action 
of  nitrosyl  sulphate  on  an  aqueous  solution  of  orthocresol,5  or 
by  adding  hydroxylamine  hydrochloride  to  a  dilute  solution  of 
toluquinone.6  It  is  only  slightly  soluble  in  cold,  more  readily  in  hot 

1  Hagen  and  Zincke,  Bcr.  Deutsch.  Chem.  Ges.  xvi.  1558. 

2  Southworth,   Ann.   Chem.  Pharm.  clxviii.  274  ;  Bergmann,  ibid.   clii.    248  ; 
Brauninger,  ibid,  clxxxv.  352  ;  Knapp  and  Schultz,  ibid.  ccx.  176. 

8  Hayduck,  ibid,  clxxii.  209. 

4  Canzoneri  and  Spica,  Bcr.  Deutsch.  Chem.  Ges.  xvi.  793. 

8  Nolting  and  Kohn,  ibid.  xvii.  370. 

6  Goldschmidt  and  Schmidt,  ibid.  xvii.  2063. 


TOLUQUINONOXIME  COMPOUNDS.  51 

water,  from  which  it  crystallizes  in  long,  white  needles,  melting 
at  134° — 135°,  It  forms  a  reddish  brown  solution  in  dilute 
alkalis,  and  is  thrown  down  by  acids  as  a  white,  flocculent 
precipitate. 

Potassium  a-toluquinonoximate,  C6H3(CH3)O(NOK),  is  ob- 
tained by  the  addition  of  an  ethereal  solution  of  toluquinone- 
oxime  to  a  solution  of  potassium  ethylate,  as  a  yellowish 
green  precipitate,  which  crystallizes  from  acetone  in  brown 
needles. 

Sodium  a-toluquinonoximate,  C6H3(CH3)0(NONa)  +  3H2O,  is 
a  dark  green  precipitate  which  crystallizes  from  acetone  in  short, 
brown  needles,  and  forms  a  reddish  brown  solution  in  water ;  it 
detonates  when  heated. 

Toluquinonoxime  gives  Liebermann's  reaction  with  phenol 
and  sulphuric  acid ;  potassium  ferricyanide  oxidizes  it  to 
/3-nitro-orthocresol,  and  nitric  acid  to  dinitro-orthocresol,  while  it 
is  converted  into  #-amido-orthocresol  by  reduction. 

a-Toluquinone  chlorimide,  C6H3(CH3)O(NC1),  is  formed  in  an 
analogous  manner  to  quinone  chlorimide  when  a  concentrated 
solution  of  bleaching  powder  is  added  to  a  dilute  hydrochloric  acid 
solution  of  ry-amido-orthocresol ;  the  liquid  first  becomes  coloured 
cherry-red,  changing  to  golden-yellow,  the  chlorimide  then 
separating  out.  It  crystallizes  from  benzene  in  yellow  needles, 
which  melt  at  87° — 88°  and  detonate  at  higher  temperatures. 
When  boiled  with  water  it  volatilizes,  a  portion  being  simul- 
taneously decomposed  into  a-toluquinone  and  brown,  amorphous 
bodies ;  it  also  gives  Liebermann's  reaction.1 

ft- Toluquinonoxime,  or  Nitrosometacresol,  C6H3(CH3)0(NOH), 
has  been  prepared  by  boiling  nitrosodimethylmetatoluidine ;  it 
is  slightly  soluble  in  hot  water,  from  which  it  crystallizes  in 
small,  colourless  needles,  while  it  is  deposited  from  solution  in 
ether  or  acetic  acid  in  thick  needles  or  prisms,  decomposing  at 
140°— 150°. 

P-Toluquinonoxime  acetate,  C6H3(CH3)0(NO.C2H3O),  is  ob- 
tained by  the  action  of  acetic  anhydride  on  the  compound 
just  described ;  it  crystallizes  from  alcohol  in  prisms  melting  at 
92°. 

/3-Toluquinonoxime  gives  Liebermann's  reaction  in  a  most 
characteristic  manner;  nitric  acid  oxidizes  it  to  trinitrometa- 
cresol.2 

1  Hirsch,  Bcr.  Dcutsch.  Chem.  Gw.  xviii.  1514. 

2  Wursterand  Riedel,  ibid.  xii.  1799. 


52  AROMATIC  COMPOUNDS. 

The  following  formulae  explain  the  isomerism  of  the  two 
toluquinonoximes : 

13 
CO  CO 

HC     C— CH3  HC     CH 

II       II  II       II 

HC      CH  HC     C— CH3 

v  \/ 

C  C 

II  II 

NOH.  NOH. 

Paracresol  does  not  form  a  nitroso-compound  or  quinonoxime, 
since  the  methyl  group  is  situated  in  the  para-position. 

Hydroxytoluquinonoxime,  C6H2(CH3)(OH)0(NOH).  This 
compound,  which  is  also  called  nitroso-orcinol,  is  obtained  by 
evaporating  a  solution  of  12  grammes  of  orcinol  and  4  grammes 
of  caustic  soda  to  a  syrup,  and  gradually  adding  12  grammes 
of  amyl  nitrite  to  the  cold  mass  with  constant  stirring;  the 
mixture  is  then  gently  heated  on  the  water-bath  until  a  small 
portion  dissolved  in  water  gives  a  red  precipitate  with  sulphuric 
acid.  The  fused  mass  is  then  dissolved  in  water  and  precipitated 
with  dilute  sulphuric  acid.  Nitroso-orcinol  crystallizes  from  alcohol 
in  small  dark  red  prisms,  which  become  coloured  black  at  110° 
without  melting.1  It  has  the  following  constitution  : 

CO 

/\ 

HC      CH 

II        II 
OH— C      C— CH3 


NOH. 

Azo-orcin,  C14HUN03.  Weselsky  obtained  this  compound  by 
the  action  of  his  reagent  on  an  ethereal  solution  of  orcinol ; 2  it  is 
also  formed  when  orcinol  is  heated  on  the  water-bath  with  nitroso- 
orcinol  and  sulphuric  acid  (Brunner  and  Kramer).  It  crystal- 
lizes in  small,  brownish  red  prisms  which  dissolve  in  alkalis 
forming  a  deep  purple-coloured  solution  with  a  splendid  orange- 

1  Brunner  and  Kramer,  Ber.  Deutsch.  Chem.  Ges.  xvii.  1879. 

2  Ibid.  vii.  439. 


METHYLPYROGALLOL.  5.3 

red    fluorescence;   acids  precipitate   it   from   this   as   a  scarlet 
powder. 

Its  formation  is  quite  analogous  to  that  of  azoresorcin, 
C12H9NO4  (Part  III.  p.  176),  but  it  is  not  homologous  with  this 
substance.  The  homologous  compound  is,  however,  first  formed 
and  is  converted  into  azo-orcin  with  loss  of  water;  the  latter 
compound  may  probably  possess  the  following  constitution  : 

0  O  O 

CH3.C6H3<    >NC6H2(CH3)<   >C6H2(CH3)N<   >C6H3CH3. 
O  O  O 

Liebermann  obtained  a  similar  colouring  matter  by  gradually 
adding  40  grammes  of  his  reagent  to  a  solution  of  10  grammes 
of  orcinol  in  10  grammes  of  sulphuric  acid.1  Another  colouring 
matter  is  simultaneously  formed  but  can  easily  be  separated,  as 
it  forms  a  sodium  salt  which  is  insoluble  in  alcohol,  while  that 
of  the  former  forms  a  purple-red  solution  with  a  cinnabar-red 
fluorescence.  The  colurring  matter,  C22H21N06,  separated  from 
this  solution  by  the  addition  of  an  acid,  is  an  amorphous  mass 
with  a  beetle-green  fluorescence,  the  aqueous  alkaline  solution  of 
which  has  a  brownish  red  fluorescence.  The  formation  of  this 
compound  corresponds  exactly  to  that  of  Liebermann's  phenol 
colouring-matter,  and  its  constitution  is  therefore  the  following  : 

OH 

H0  O.CH—  CH 


362 
HO/  \O.C6H3—  CH3 

OH. 

The  second  colouring  matter,  C22H21N07,  is  an  oxidation 
product  of  the  former,  which  it  resembles  very  closely  ;  its  violet 
Ikaline  solution,  however,  does  not  fluoresce  (Brunner  and 
ler). 


TRIHYDROXYTOLUENES,  C6H2(CH3)(OH)3. 

2045  Mcthylpyrogallol,  or  Methylpyro  gallic  acid,  is  the  only 
mown  compound  of  this  group.  Its  dimethyl  ether  occurs, 
)gether  with  the  same  ethers  of  pyrogallol  and  propylpyrogallol 

1  Ber.  Deutsch.  Chem.  Gcs.  vii.  1110. 
235 


54  AROMATIC  COMPOUNDS. 

in  the  fraction  of  beech-wood-tar  creosote  which  dissolves  in 
alkalis  and  boils  at  between  255°  and  270°.  In  order  to 
separate  them,  the  mixture  is  heated  with  benzoyl  chloride,  the 
benzoic  ethers  separated  by  fractional  crystallization  and  then 
decomposed  by  alcoholic  potash. 

MetJiylpyrogallol  dimethyl  ether,  C6H2(CH3)(OCH3)2OH,  is  a 
crystalline  substance,  melts  at  36°,  and  boils  at  265°.  On  heating 
with  concentrated  hydrochloric  acid,  methylpyrogallol  is  obtained  ; 
this  closely  resembles  pyrogallol,  and  on  heating  sublimes  in 
needles,  which  melt  at  129°.  Its  aqueous  solution  is  coloured 
brown  by  ferrous  sulphate,  and  its  alkaline  solution  rapidly  turns 
brown  in  the  air.1 


AMIDO-DERIVATIVES  OF  TOLUENE. 

AMIDOTOLUENES,   OR   TOLUIDINES,   C6H4(CH3)NH2. 

2046  The  history  of  these  compounds  goes  hand  in  hand 
with  that  of  the  nitrotoluenes.  Hofmann  and  Muspratt  reduced 
crude  nitrotoluene  by  repeated  treatment  with  alcoholic  am- 
monium sulphide  and  obtained  the  product  free  from  unaltered 
nitrotoluene  by  washing  well  with  water,  treating  with  hydro- 
chloric acid  and  distilling  the  liquid,  after  the  removal  of  all 
alcohol  by  evaporation,  with  caustic  soda ;  they  thus  obtained  an 
oily  liquid  which  solidified  after  some  time  to  a  crystalline  mass, 
and  to  this  new  organic  base  they  gave  the  name  toluidine.  The 
aqueous  distillate  obtained  in  the  preparation  contained  some 
ammonia  and  a  not  inconsiderable  amount  of  base  in  solution ; 
the  whole  distillate  was  therefore  treated  with  an  excess  of 
ammonium  oxalate,  evaporated  to  dryness  on  the  water-bath 
and  the  residue  extracted  with  boiling  absolute  alcohol, 
ammonium  oxalate  being  in  this  way  left  undissolved.  On 
cooling,  toluidine  oxalate  separated  out  in  white  crystals,  which 
were  washed,  dissolved  in  hot  water,  and  decomposed  with 
concentrated  caustic  potash  solution.  The  oil  which  separated 
out  solidified  on  cooling  to  a  radiating  crystalline  mass  of 
pure  toluidine,  the  properties  of  which  were  then  accurately 
investigated. 

After  the  discovery  of  the  aniline  dyes,  aniline  and  toluidine, 

1  Hofmann,  Ber.  Deutsch.  Chem.  Ges.  xii.  1371. 


TOLUIDINES.  55 


or  rather  a  mixture  of  the  two  called  aniline  oil,  was  manu- 
factured on  the  large  scale;  and  Rosenstiehl  found  in  this 
mixture  a  liquid  base,  isomeric  with  the  ordinary  toluidine,  to 
which  he  gave  the  name  of  pseudotoluidine.  We  have  already 
pointed  out  that  the  three  nitrotoluenes  are  formed  in  varyino- 
quantities  by  the  nitration  of  toluene.  If  concentrated  acid 
be  employed  without  cooling,  paranitrotoluene  is  chiefly  formed, 
and  this  yields  on  reduction  the  solid  paratoluidine  obtained  by 
Hofmann  and  Muspratt.  If,  however,  a  weaker  acid  be  employed, 
and  the  temperature  be  kept  low,  more  of  the  ortho-compound  is 
formed,  and  it  is  from  this  that  the  pseudotoluidine  is  derived ; 
a  small  quantity  of  metanitrotoluene  being,  however,  invariably 
produced. 

The  toluidines  are  manufactured  on  a  large  scale ;  the  para- 
compound  is  that  which  is  most  readily  obtained  in  the 
pure  state,  as  the  purification  of  paranitrotoluene  offers  no 
difficulties,  whilst  it  is  very  difficult,  working  on  the  large 
scale,  to  obtain  an  orthonitrotoluene  free  from  paranitrotoluene, 
so  that  ordinary  commercial  orthotoluidine  always  contains  some 
of  the  para-compound  together  with  metatoluidine  and  generally 
a  little  aniline. 

The  amount  of  paratoluidine  in  such  a  mixture  can  readily  be 
determined  by  means  of  the  different  solubilities  of  the  oxalates 
in  ether;  at  15° 

Acid  paratoluidine  oxalate  requires  6660  parts  of  ether, 
Acid  orthotoluidine  oxalate      „          200  „ 

for  solution.  A  small  quantity,  about  0'2  grms.,  of  the  mixture 
is  dissolved  in  80  grms.  of  ether  and  titrated  with  a  solution  of 
T062  grms.  of  oxalic  acid  in  250  c.c.  of  ether  until  no  further 
precipitate  is  formed.  Each  cubic  centimetre  of  the  solution 
employed  corresponds  to  0'005  grms.  of  paratoluidine.1  The 
end  of  the  reaction  can  easily  be  recognised  by  the  acid 
reaction  of  the  solution  towards  litmus-paper  as  soon  as  the 
orthotoluidine  oxalate  commences  to  be  formed.  The  deter- 
mination is  rendered  still  more  accurate  by  adding  an  excess  of 
oxalic  acid  solution  to  the  solution  of  the  bases,  filtering  from 
the  precipitate,  evaporating  the  ether,  dissolving  the  residue  in 
a  little  water  and  determining  the  excess  of  oxalic  acid  by 
decinormal  caustic  soda  solution.2 

1  Rosenstiehl,  Ann.  Chim.  Phys.  (1872),  xxvi.  249. 

2  Lorenz,  Ann.  Chcm.  Pharm.  clxxii.  190. 


56  AROMATIC  COMPOUNDS. 

In  order  to  separate  larger  quantities  of  the  base,  an  amount 
of  oxalic  or  sulphuric  acid  equivalent  to  the  paratoluidine 
present  is  added,  and  the  whole  distilled  with  steam;  ortho- 
toluidine  alone  passes  over,  and  the  para-compound  as  the 
stronger  base  remains  behind  in  /combination  with  the  acid 
(Rosenstiehl). 

Ihle  dissolves  the  bases  in  ether,  precipitates  with  an  ethereal 
solution  of  oxalic  acid  and  from  time  to  time  treats  a  small 
portion  of  the  solution  with  acetyl  chloride.  The  product  is 
re-crystallized  from  hot  water  and  its  melting-point  observed. 
Since  acetparatoluide  melts  at  145°,  and  acetorthotoluide  at 
107°,  the  point  at  which  all  the  paratoluidine  is  removed  can 
readily  be  recognised.1 

Binschedler  gives  the  following  process  for  the  treatment  of  a 
mixture  of  30  per  cent,  of  paratoluidine  and  70  per  cent,  of  ortho- 
toluidine  which  comes  into  the  market  under  the  name  of 
"aniline  lourde  spdciale" :  10  kilos,  of  the  mixture  of  bases  are 
gradually  added  to  a  solution  of  2' 5  kilos,  of  oxalic  acid  in 
25  litres  of  boiling  water  to  which  6  litres  of  hydrochloric  acid 
of  specific  gravity  1*15  have  been  added,  the  mixture  being 
then  heated  to  the  boiling  .point,  and  constantly  stirred  until 
it  has  cooled  down  again  to  60°.  The  crystalline  precipitate 
which  consists  of  pure  paratoluidine  oxalate,  is  rapidly  filtered 
off,  pressed,  and  washed  with  a  little  water ;  2  kilos,  of  oxalic 
acid  are  now  added  to  the  filtrate,  a  mixture  of  the  oxalates 
being  thus  precipitated.  When  oxalic  acid  produces  no  further 
precipitate  in  the  mother-liquor,  it  is  distilled  with  caustic 
soda,  orthotoluidine  being  obtained  which  contains  a  very  small 
quantity  of  paratoluidine  and  only  traces  of  aniline.2 

Another  method  of  separation,  which  has  been  patented  by 
Leo  Levy,  depends  upon  the  behaviour  of  the  hydrochlorides  of 
the  bases  towards  sodium  phosphate.  Aniline  hydrochloride 
gives  the  following  reaction  : 

Na2HPO4 + 2C6H6NH3C1  =  2NaCl  +  (C6H5.NH3)2HP04. 

Paratoluidine  hydrochloride  behaves  in  a  similar  manner, 
while  the  orthotoluidine  salt  yields  80  per  cent,  of  the  free  base 
and  20  per  cent,  of  the  acid  phosphate : 

1)  C7H7.NH2HC1  +  Na2HP04  =  C7H7.NH2  +  NaH2P04  +  NaCl. 

2)  C7H7.NH2HC1  +  NaH2P04  =  (C7H7.NH3)H2PO4 + NaCl. 

1  Journ.  PraTct.  Chem.  [2]  xiv.  449.         2  Ber.  Dcutsch.  Chem    Gcs.  vi.  448. 


ORTHOTOLUIDINE.  57 


The  mixed  hydrochlorides  are  therefore  treated  with  a 
solution  of  sodium  phosphate;  the  crystalline  mass  which  is 
formed  is  then  dissolved  by  warming,  and  the  orthotoluidine 
removed  from  the  surface.  On  cooling,  the  phosphates  of  aniline 
and  paratoluidine  separate  out  completely,  while  the  phosphate  of 
orthotoluidine  remains  in  solution.  The  sodium  phosphate  can 
be  recovered  after  separation  of  the  bases ;  sodium  arsenate  may 
also  be  employed.1 

Another  process  for  the  separation  of  orthotoluidine  from 
aniline  oil  by  means  of  the  nitrate  has  been  described  by 
L.  Schad.2 

2047  Orthotoluidine,  discovered  by  Rosenstiehl,3  is  formed  by 
the  reduction  of  orthonitrotoluene  and  by  the  distillation  of 
paramidotoluic  acid  with  lime.4  It  is  a  colourless  liquid  re- 
sembling aniline  very  closely ;  it  soon  becomes  brown  in  the  air 
or  on  exposure  to  light,  boils  at  198' 5°,  has  a  specific  gravity  of 
1-003  at  20'2°,  and  does  not  solidify  at  -  20°.  A  solution  of  this 
base  in  monohydrated  sulphuric  acid  gives  a  blue  colouration  with 
a  solution  of  chromium  trioxide  in  sulphuric  acid  of  the  same 
strength ;  the  colour  changes  to  a  stable  reddish  violet  on 
dilution.  Nitric  acid  added  to  the  sulphuric  acid  solution  gives 
an  orange  to  brown  colouration,  passing  into  yellow  on  the  addi- 
tion of  water.  If  the  base  be  dissolved  in  ether  and  an  equal 
volume  of  water  added,  the  lower  layer  of  the  solution  gives 
a  yellow  to  brown  colouration  with  dilute  sulphuric  acid.  If  the 
ethereal  layer  be  now  removed  and  shaken  with  dilute  sulphuric 
acjd,  it  becomes  coloured  a  stable  reddish  violet  (Lorenz). 

Orthotoluidine  further  differs  from  its  isomerides  in  giving  a 
green  colouration  with  ferric  chloride  and  a  little  paradiamido- 
benzene.  This  reaction  is  so  delicate  that  a  solution  containing 
1  in  10,000  gives  a  tolerably  deep  colouration,  and  a  solution  only 
one-tenth  as  strong  as  this  assumes  a  distinct  shade  of  green.6  All 
commercial  aniline  gives  this  reaction,  as  also  does  that  obtained 
by  the  distillation  of  indigo  with  caustic  potash,  which  was  con- 
sidered to  be  chemically  pure  until  Rosenstiehl  proved  that  it 
contained  orthotoluidine. 

The  salts  of  orthotoluidine  have  been  investigated  by  Beilstein 
and  Kuhlberg. 

1  Bcr.  Dcutsch.  Chem.  Ges.  xvi.  980.  2  Ibid.  vi.  1361. 

3  Zeitschr.  Chem.  [2]  iv.  557. 

1  Beilstein  and  Kuhlberg,  Ann.  Chem.  Pharm.  clvi.  75. 

5  Monnet,  Reverdin  and  Nblting,  Ber.  Deutsch.   Chem.   Ges.  xi.    2278.     See 
also  Reinhardt  and  Stadel,  ibid.  xv.  29. 


58  AROMATIC  COMPOUNDS 

Orthotoluidine  hydrochloride,  C7H9NClH-f  H20,  forms  white 
crystalline  crusts,  37'4  parts  of  which  dissolve  in  100  parts  of 
water  at  15'5° ;  it  is  still  more  readily  soluble  in  alcohol. 

Orthotoluidine  hydrobromide,  C7H9N.BrH,  crystallizes  very 
easily  in  large  rhombic  prisms  ;  the  hydricdide  resembles  it,  but 
is  partially  decomposed  by  water.1 

Orthotoluidine  sulphate,  (C7H9N)2H2S04,  forms  small  crystals 
which  become  coloured  violet  to  green  in  the  air;  100  parts  of 
water  at  22°  dissolve  7*5  parts.  It  is  only  slightly  soluble  in 
alcohol. 

Orthotoluidine  ni/rate,  C7H9N.HNO3,  crystallizes  in  small 
plates  ;  100  parts  of  water  at  19'2°  dissolve  lO'Ol  parts. 

Orthotoluidine  oxalate  crystallizes  in  small  colourless  plates-, 
100  parts  of  water  at  21°  dissolve  2'38  parts. 

Hethylorthotoluidine,  C6H4(CH3)N(CH3)H,  is  formed  when 
750  grms.  of  Orthotoluidine  are  heated  for  a  day  to  200°—  220° 
with  400  grms.  of  methyl  alcohol  and  700  grins,  of  .hydrochloric 
acid.  The  product  is  distilled  in  steam,  and  every  100  grms.  of 
distillate  dissolved  in  120  grms.  of  hydrochloric  acid  and  300 
grms.  of  water,  the  solution  being  then  treated  with  a  con- 
centrated solution  of  40  grms.  of  sodium  nitrite,  the  mixture 
being  cooled  and  well  agitated.  The  methylorthotolylnitros- 
amine,  C6H4(CH3)N(CH3)NO,  formed,  which  is  very  similar  to 
methylnitroso-aniline,  is  extracted  with  ether,  reduced  with  tin 
and  hydrochloric  acid,  decomposed  with  caustic  soda,  and  distilled 
with  steam. 

Methylorthotoluidine  is  a  colourless  liquid  which  rapidly 
becomes  coloured  violet-brown  in  the  air,  and  boils  at 
207°— 2080.2 

Dimethylorthotoluidine,  C6H4(CH3)N(CH3)2.  Thomsen  ob- 
tained this  compound  by  the  distillation  of  trimethyltolyl- 
ammonium  hydroxide ;  it  is  also  formed,  together  with  other 
products,  when  trimethylphenylammonium  iodide  is  heated  to 
220° — 23 0°.3  It  can  readily  be  prepared  pure  by  heating  750 
grms.  of  Orthotoluidine  for  two  days  with  670  grms.  of  methyl 
alcohol  and  700  grms.  of  hydrochloric  acid,  the  product  being 
repeatedly  rectified  (Monnet,  Reverdin  and  Nolting).  It  is  a 
colourless  liquid  which  has  a  characteristic  aromatic  odour  and 
boils  at  183°. 

1  Stadel,  Ber.  Deutsch.  Chem.  Ges.  xvi.  28. 

2  Monnet,  Reverdin  and  Nolting,  Bcr.  Deutsch.  Chem.  Ges.  xi.  2278.     See  also 
Reinhardt  and  Stadel,  ibid.  xv.  29.  3  Hofmann,  ibid.  x.  1585. 


DERIVATIVES  OF  ORTHOTOLUIDINE.  59 

Trimethylorthotolylammonium  iodide,  C6H4(CH3)N(CH3)3I,  is 
formed  by  the  continued  action  of  methyl  iodide  on  ortho- 
toluidine,1  and  crystallizes  in  large  needles  which  assume  a  faint 
purple  tint  in  the  air. 

Boiling-point.  • 
Ethylorthotoluidine,      C7H9N(C2H5)H,      liquid     213°— 214° 

Diethylorthotoluidine,2  C7H9N(C2H5)2  „         208°— 209°. 

Phenylorthotolylamine,  C6H5.NH(C7H7),  is  formed,  together 
with  diphenylamine  and  di-orthotolylamine,  when  orthotoluidine 
is  heated  with  aniline  hydrochloride  to  280°.3  It  is  a  crystalline 
substance  which  melts  at  41°,  boils  at  297° — 299°,  and  gives  a 
violet-blue  colouration  with  nitric  acid. 

Di-orthotolylamine,  (C7H7)2NH,  is  a  liquid  boiling  at  304° — 
308°. 

Acetorthotoluide,  C7H7.N(C2H3O)H,  forms  long  needles,  melts 
at  107°  and  boils  at  296°;  100  parts  of  water  at  19°  dissolve 
0*86  parts  (Beilstein  and  Kuhlberg). 

Orthotolyl  carbamide,  (C7H7)NH.CO.NH2,  is  formed  by  the 
ion  of  potassium  cyanate  on  orthotoluidine  hydrochloride  ;  it  is 
>luble  in  cold  water,  moderately  soluble  in  hot  water,  and 
lily  in  alcohol,  crystallizing  in  tablets  which  melt  at  1850.4 
Di-orthotolyl  carbamide,  (C7H7)2NCO.NH2,  is  formed  by  the 
action  of  carbonyl  chloride  on  orthotoluidine,  by  heating  the 
latter  with  urea,5  or  by  heating  its  hydrochloride  with  cyanamide 
to  100°.6  It  is  insoluble  in  water,  but  slightly  soluble  in  alcohol, 
rystallizing  in  fine  needles  which  melt  at  243°. 
Orthotolyl  carbamide,  or  Orthotolyl  isocyanate,  CON.C6H4.CH3. 
rhen  orthotoluidine  is  acted  upon  by  chlorocarbonic  ether, 
rtolyl  urethane,  NH(C7H7)CO.OC2H5,  is  formed  in  crystals 
lelting  at  46°,7  and  on  heating  with  phosphorus  pentoxide  is 
>n verted  into  the  isocyanate,  which  is  a  liquid  boiling  at  186° 
and  possessing  a  penetrating  odour  (Girard).  Water  decom- 
poses it  with  formation  of  ditolyl  carbamide. 

Orthotolyl  thiocarbamide,  (C7H7)HN(CS)NH2,  is  obtained  by 
the  action  of  ammonia  on  orthotolyl  mustard  oil ;  it  melts  at 
155°  and  is  readily  soluble  in  boiling  water.8 

1  Thomsen,  Ber.  Deutsch.  Chcm.  Ges.  x.  1586. 

2  Stadel  and  Reinhardt,  loc.  cit.  ;  Norton,  Ann.  Chcm.  Journ.  vii.  118. 

3  Girard  and  Willm,  Bull.  Soc.  CMm.  xxv.  248. 

4  Cosack,  Ber.  Deutsch.  Chem.  Ges.  xiii.  1089. 

6  Girard,  ibid.  vi.  444.  «  Berger,  ibid.  xii.  1859. 

7  Lachmann,  ibid.  xii.   1349  ;  Neville  and  Winther,  ibid.  xii.  2324. 

8  Staats,  ibid.  xiii.  135. 


60  AROMATIC  COMPOUNDS. 

Di-orthotolyl  thiocarbamide,  (CrH7.NH)2CS,  is  obtained  by  the 
action  of  carbon  disulphide  on  an  alcoholic  solution  of  orthotolu- 
idine.1  It  crystallizes  from  hot  alcohol  in  needles  melting  at  158°. 

Orthotolyl  thiocarbamide,  or  Orthotolyl  mustard  oil,  CSN.C6H4. 
CH3,  is  formed  when  the  compound  just  described  is  boiled 
with  fuming  hydrochloric  acid.  It  is.  a  strongly  refractive  liquid, 
boiling  at  239°  and  possessing  a  pungent  odour  (Girard). 

It  combines  with  aniline  forming  phenylorthotolyl  thiocarbamide, 
(C6H5)NH(CS)NH(C7Hr),  which  has  also  been  prepared  from 
orthotoluidine  and  phenyl  mustard  oil  (Staats) ;  it  forms  long 
needles  melting  at  139°,  and  is  decomposed  by  hydrochloric 
acid  into  aniline  and  tolyl  mustard  oil. 

2048  Metatoluidine  was  obtained  by  Beilstein  and  Kuhlberg 
by  the  reduction  of  metanitrotoluene,2  which  is  best  effected  by 
means  of  stannous  chloride  and  hydrochloric  acid  (Cosack) 
According  to  Widmann,  it  is  also  formed  when  metanitrobenzyl- 
ene  chloride,  C6H4(NO2)CHC12,  obtained  by  the  action  of  phos- 
phorus chloride  on  metanitrobenzaldehyde,  is  reduced  with  zinc 
dust  and  hydrochloric  acid.3 

It  is  a  colourless  oily  liquid  which  has  a  specific  gravity  of  0'998 
at  25°,  and  becomes  converted  into  a  brown  resinous  mass  when 
exposed  to  the  air  (Lorenz)  ;  it  boils  at  197°  and  does  not  solidify 
even  at  —13°.  If  it  be  dissolved  in  monohydrated  sulphuric 
acid  and  treated  with  a  sulphuric  acid  solution  of  chromium 
trioxide,  a  yellowish  brown  liquid  is  obtained  which  becomes 
brown  on  gentle  heating,  and  is  coloured  greenish  yellow  by  the 
addition  of  a  little  water,  a  larger  quantity  rendering  it  colour- 
less. Nitric  acid  added  to  the  original  solution  produces  a 
reddish  colouration  which  rapidly  becomes  a  deep  blood-red,  and 
then  a  dark  dirty-red,  and  is  converted  into  orange  by  the 
addition  of  water.  When  a  solution  of  the  base  in  equal 
volumes  of  ether  and  water  is  treated  with  bleaching  powder 
solution,  the  aqueous  layer  is  coloured  brownish  yellow  and 
becomes  turbid,  while  the  ether  exhibits  a  reddish  fluorescence ; 
if  the  ether  be  poured  off  and  shaken  up  with  water  and  a 
drop  of  dilute  sulphuric  acid,  the  water  becomes  coloured  a 
faint  violet. 

The  salts  of  metatoluidine  have  been  investigated  by  Lorenz.4 

1  Girard,  Ber.  Deutsch.  Chem.  Ges.  iv.  985  ;  Berger,  ibid.  xii.  1854. 

2  Ann.  Chem.  Pharm.  clvi.  83. 

3  Ber.  Deutsch.  Chem.  Ges.  xiii.  676  ;  xiv.  2583.     See  also  ibid.  xiv.  1403. 

4  Ann.  Chem.  Pharm.  clxxii.  177. 


METATOLUIDINE.  61 


Metatoluidine  hydrochloride,  C7H9N.C1H,  crystallizes  from  a 
very  concentrated  aqueous  solution  in  thin  tablets,  and  from 
alcohol  in  thin,  pale  red  crusts. 

Metatoluidine  sulphate,  (C7H9N)2S04H2,  crystallizes  in  long, 
transparent,  light  red,  radiating  needles,  which  are  insoluble  in 
ether,  slightly  soluble  in  alcohol,  and  more  readily  in  water,  100 
parts  of  which  at  14°  dissolve  6*25  parts. 

Metatoluidine  nitrate,  C7H9N.NO3H,  crystallizes  in  large,  pale 
red,  rhombic  plates,  16*42  parts  of  which  dissolve  in  100  parts  of 
water  at  15'5°;  it  is  still  more  soluble  in  alcohol,  but  only 
slightly  soluble  in  ether. 

Acid  mctatoluidine  oxalate,  C7H9N.C2O4H2,  forms  warty  masses 
consisting  of  fine  silky  needles,  which  are  only  slightly  soluble 
in  ether,  alcohol  and  water;  100  parts  of  the  latter  at  13° 
dissolve  2'65  parts.  When  its  solution  is  warmed  with  meta- 
toluidine,  the  salt,  (C7H9N)3(C204H2)2,  separates  out  in  a  mass 
of  rhombic  plates  which  are  still  less  soluble  than  the  mono- 
acid  salt.  If  an  excess  of  metatoluidine  be  added  in  warm 

Icoholic  solution  to  oxalic  acid,  small  rhombic  plates  separate 
nit  on  cooling  in  such  quantity  that  the  liquid  solidifies  to  a 

}lly.     These  crystals  appear  to  be  the  hydrated  normal  salt; 
washing  with  alcohol  and  drying,  they  possess  the  appear- 

ice   of  cholesterin;   they  are  scarcely  wetted   by   water   and 
heated  with  it  for  a  long  time  decompose  into  the  acid 

It  and  the  free  base. 

Methylmetatoluidine,  C6H4(CH3)N(CH3)H,  is  formed,  together 

rith  dimethylmetatoluidine,  by  the  action  of  methyl  iodide  on 

ie  primary  base.     The  product  is  extracted  with  ether  and 
jd  from  unattacked  metatoluidine  by  the  addition  of  sulphuric 

jid,  an  alkali  is  then  added,  the  ether  distilled  off  and  the  residual 

il  dried  and  heated  with   acetic   anhydride.     On   distillation, 

jetic  acid  and  acetic  anhydride  first  come  over,  followed  by 
limethyltoluidine  and  finally  by  methylacetoluide,  boiling  above 

550°.  This  is  purified  by  repeated  distillation  and  decomposed 
by  heating  with  dilute  sulphuric  acid,  pure  methylmetatoluidine 
being  thus  obtained  ;  it  is  a  colourless  liquid  which  boils  at 
206° — 207°,  and  possesses  a  characteristic  aromatic  odour. 

Dimethylmetatoluidine,  C6H4(CH3)N(CH3)2,  boils  at  215° 
(Wurster  and  Eiedel),  and  has  a  characteristic  odour  differing 
from  that  of  its  isomerides,  but  resembling  that  of  dimethyl- 
aniline.1 

1  Nolting,  Ber.  Deutsch.  Ckcm.  Gcs.  xi.  2278. 


62  AROMATIC  COMPOUNDS. 

Nitrosodimcthylmdatoluidine,  C6H8NO(CH3)N(CH3)2,  is  formed 
on  the  addition  of  sodium  nitrite  to  a  cooled  solution  of  di- 
methylmetatoluidine  in  hydrochloric  acid.  The  hydrochloride 
thus  prepared  crystallizes  from  a  hot,  acidified  solution  in  light 
yellow  to  greenish  yellow  needles  which  are  only  slightly  soluble 
in  cold  water.  Sodium  carbonate  liberates  the  free  base,  which 
crystallizes  from  ether  in  small,  green  plates  or  long  needles, 
melting  at  92°.  It  is  precipitated  by  petroleum  ether  from  a 
solution  in  chloroform  in  moss-green  needles,  and  separates  from 
benzene  in  large,  dark  green  crystals  containing  benzene  of 
crystallization,  which  they  lose  in  the  air  together  with  their 
colour  and  lustre.  All  its  solutions  are  coloured  deep  green.  It 
crystallizes  from  water  in  small,  lustrous  green  plates. 

Like  nitrosodimethylaniline,  it  forms  deep  steel-blue  coloured 
compounds  with  aniline,  orthotoluidine,  &c.,  and  does  not  give 
Liebermann's  reaction  in  the  cold.  Boiling  dilute  caustic  soda 
converts  it  into  nitrosocresol ;  potassium  permanganate  oxidizes 
it  to  nitrodimctJiylmetatoluidine,  C6H8N02(CH3)N(CH3)2,  which 
crystallizes  in  long  yellow  needles,  melting  at  84°.  It  is  re- 
duced by  tin  and  hydrochloric  acid  to  dimethyldiamidotoluene 
C6H3(CH3)(NH2)N(CH3)2. 

Since  the  two  isomerides  of  dimethyltoluidine  give  no 
nitroso-compounds,  the  presence  of  metatoluidine  can  readily 
be  detected  in  orthotoluidine,  and  its  amount  approximately 
determined ;  to  effect  this  the  hydrochlorides  are  prepared,  the 
greater  part  of  the  orthotoluidine  salt  removed  by  crystallization, 
the  mother-liquor  evaporated  to  dryness,  and  the  residue  heated 
with  methyl  alcohol ;  the  almost  insoluble  nitrosodimethylmeta- 
toluidine  is  then  prepared  directly  from  the  mixture  of  dimethyl- 
toluidines  thus  obtained.  The  two  bases  can  also  be  separated 
by  fractional  distillation,  since  the  ortho-compound  boils  at  183C 
and  the  meta-compound  at  2150.1 

Metaditolylamine,  (C6H4.CH3)2NH,  is  formed  when  meta- 
toluidine is  heated  with  its  hydrochloride.  It  is  a  thick,  oily, 
light  yellow  liquid  which  becomes  coloured  brown  in  the  air  and 
boils  at  319°—  320°.2 

Acetmetatolmde,  C6H4(CH3)N(C2H30)H,  crystallizes  on  the 
gradual  evaporation  of  its  aqueous  solution  in  long  needles 
united  to  form  bushy  aggregates ;  it  melts  at  6 5 '5°,  and  boils  at 


1  Wurster  and  Kiodel,  Ber.  Deutsch.  Chem.  Ges.  xii.  1796. 

2  Cosack,  ibid.  xiii.  1088. 


PARATOLUIDINE.  63 


303°.  100  parts  of  water  at  13°  dissolve  0'44  parts  (Beilstein 
and  Kuhlberg). 

Metatolyl  carbamide,  (C6H4.GH3)HN.CO.NH2,  has  been  pre- 
pared from  metatoluidine  and  potassium  cyanate  ;  it  crystallizes 
from  water  in  small  plates,  and  from  alcohol  in  tablets  or 
needles,  melting  at  142°. 

Dimetatolyl  carbamide,  CO(NH.C7H7)2.  When  metatoluidine 
acted  upon  by  chlorocarbonic  ether,  metatolyl  urethane, 
(C7H7)HKCO.OC2H5,  is  formed ;  this  is  a  liquid  which  on 
distillation  in  the  moist  state  yields  alcohol,  carbon  dioxide,  and 
dimetatolyl  carbamide.  The  latter  crystallizes  from  hot  alcohol 
in  long  needles  melting  at  217°  (Cosack).1 

Metatolyl  thiocarbamide,  (C7H7)HN.CS.NH2,  is  obtained  by 
the  action  of  ammonia  on  metatolyl  thiocarbimide.  It  is  readily 
soluble  in  alcohol,  slightly  in  cold,  and  more  freely  in  hot  water, 
and  crystallizes  in  prisms  which  form  star-shaped  aggregates, 
and  melt  at  1030.2 

Dimetatolyl  thiocarbamide,  CS(NH.C7H7)2,  is  formed  when  an 
alcoholic  solution  of  metatoluidine  is  heated  for  a  long  time  with 
carbon  disulphide.  It  crystallizes  in  concentrically  arranged 
needles,  melting  at  122°,  which  are  scarcely  soluble  in  boiling 
water  but  dissolve  readily  in  alcohol. 

Metatolyl  thiocarbamide, or  Metatolyl  mustard  o^/,CSN(C6H4.CH3), 
is  formed  when  the  compound  just  described  is  heated  with 
concentrated  hydrochloric  acid.  It  is  a  colourless  liquid  which 
boils  at  244°  and  possesses  the  characteristic  smell  of  the  mustard 
oils  in  the  highest  degree  (Weith  and  Landolt.) 

2049  Paratoluidine  is  formed  by  the  reduction  of  paranitro- 
)luene  and  by  heating  methylaniline  hydrochloride  for  a  day  to 
350° ;  methylaniline  hydriodide,  on  the  other  hand,  gives  a  liquid 
toluidine,3  which  is  probably  the  ortho-compound.  It  may  also 
be  obtained  by  heating  paracresol  with  the  compound  of  zinc 
chloride  and  ammonia  to  3000.4  It  is  slightly  soluble  in 
water,  readily  in  alcohol  and  ether,  and  crystallizes  from 
hot,  dilute  alcohol  in  large,  colourless  plates  which  melt 
at  45°  and  have  a  peculiar  aromatic  odour  resembling  that  of 
aniline.  According  to  Hofmann  and  Muspratt  it  boils  at 
198°,  while  Stadeler  found  its  boiling-point  to  be  204°— 2060.5 
When  it  is  dissolved  in  monohydrated  sulphuric  acid  and  treated 

1  Ber.  Dcutsch.  Chem.  Gfes.  ;  see  also  xii.  1450. 

2  Weith  and  Landolt,  ibid.  viii.  715.  3  Hofmann,  ibid.  v.  720. 
4  Buch,  ibid.  xiv.  2345  ;  xvii.  2637.                         5  Jahresber.  1865,  409. 


64  AROMATIC  COMPOUNDS. 

with  a  solution  of  chromium  trioxide  in  acid  of  the  same  strength, 
it  is  only  coloured  yellow.  A  drop  of  nitric  acid  added  to  the 
original  solution  produces  a  blue  colouration,  which  soon  passes 
through  violet  and  red  to  brown  (Lorenz) ;  in  presence  of  aniline 
or  orthotoluidine  no  blue  colouration  is  produced,  but  the  liquid 
becomes  coloured  blood-red.  Bleaching  powder  solution  gives 
no  colouration  with  solutions  of  pure  paratoluidine ;  in  order 
therefore  to  detect  the  presence  of  aniline  in  paratoluidine,  the 
mixture  is  dissolved  in  ether,  and  shaken  up  with  an  equal 
volume  of  water,  a  solution  of  bleaching  powder  then  being  added 
drop  by  drop.  If  aniline  be  present,  the  ether  assumes  a  blue 
colour  when  the  solution  is  agitated  (Rosenstiehl). 

The  salts  of  paratoluidine  have  been  investigated  by  Hofmann 
and  Muspratt  and  by  Beilstein  and  Kuhlberg.1 

Paratoluidine  hydrochloride,  C7H9N,HC1,  crystallizes  in  white 
crusts,  which  become  coloured  in  the  air.  100  parts  of  water  at 
11°  dissolve  22'9  parts,  while  100  parts  of  89  per  cent,  alcohol 
dissolve  25  parts  at  17°. 

Paratoluidine  hydrobromide,  C7H9N,  HBr,  crystallizes  in  white 
plates ;  the  hydriodide  is  very  similar  (Reinhardt  and  Stiidel). 

Paratoluidine  sulphate,  (C7H9N)2H2SO4,  forms  lustrous,  scaly 
crystals,  5*06  parts  of  which  dissolve  in  100  parts  of  water  at 
22° ;  they  are  still  less  soluble  in  alcohol. 

Paratoluidine  nitrate,  C7H9N,  HNO3,  crystallizes,  when  its  solu- 
tion is  rapidly  cooled,  in  large  rhombic  tablets ;  when  allowed  to 
deposit  more  gradually,  it  forms  long,  transparent  needles. 
100  parts  of  water  at  23'5°  dissolve  17*7  parts;  it  is  still  more 
readily  soluble  in  alcohol. 

Acid  paratoluidine  oxalate,  C7H9N,  C204H2,  crystallizes  in 
rhombic  needles  or  prisms,  0'87  parts  of  which  dissolve  in  100 
parts  of  water  at  14° ;  alcohol  takes  up  even  less. 

Paratoluidine  phenate,  C7H9N,  C6H6O,  crystallizes  from  petro- 
leum ether  in  long  needles  melting  at  31 'I0.2 

Methylparatoluidine,  C6H4(CH3)N(CH3)H,  is  obtained  by 
passing  methyl  chloride  into  heated  paratoluidine.  The  pro- 
duct is  extracted  with  ether,  the  paratoluidine  hydrochloride 
formed  being  left  undissolved.  Any  unaltered  paratoluidine  is 
precipitated  by  dilute  sulphuric  acid,  and  the  ether  evaporated, 
a  mixture  of  methyltoluidine  and  dimethyltoluidine  being  thus 
obtained.  The  former  is  converted  by  the  action  of  acetic 

1  Ann.  Chcm.  Pharm.  clvi.  73. 

2  G.  Dyson,  Journ.  Chcm.  Soc.  1883,  i.  468. 


METHYLTOLUIDINES. 


anhydride  into  acetmethylparatolnide,  C6H4(CH3)N(C2H3O)CH3, 
which  crystallizes  from  a  mixture  of  ether  and  alcohol  in  large 
plates  melting  at  83°.  Pure  methylparatoluidine  is  then  ob- 
tained by  boiling  this  compound  with  hydrochloric  acid  and 
decomposing  the  hydrochloride  with  caustic  soda.1  It  can  be 
even  more  simply  separated  by  means  of  its  nitrosamine,  in  the 
same  way  as  its  isomeride  in  the  ortho-series.  (Monnet,  Reverdin 
and  Nolting.)  It  is  a  liquid  which  boils  at  208°  and  possesses 
an  aromatic  odour. 

Nitrosomethylparatoluidine,  C6H4(CH3)N(CH3)NO,  crystallizes 
from  a  mixture  of  ether  and  alcohol  in  large,  well-formed  prisms, 
melting  at  54°. 

Itimethylparatoluidine,  C6H4(CH3)N(CH3)2.  By  the  action  of 
lethyl  iodide  on  paratoluidine,  Thomsen  obtained  trimethyl- 
paratolylammonium  iodide,  C7H7N(CH3)3I,  which  forms  white 
crystals,  and  converted  it  by  means  of  moist  silver  oxide  into  the 
hydroxide,  which  yielded  the  base  on  distillation ; 2  it  is  a  liquid, 
which  has  a  characteristic  aromatic  odour  and  boils  at  208°. 


Ethylparatoluidine,       C7H7N(C2H5)H, 
Di-ethylparatoluidme,3  C7H7N(C2H5)2 


Boiling-point, 
liquid         217° 
229° 


Phenylparatoluidine,  or  Phenylparatolylamine,  C7H7N(C6H5)H, 
obtained  by  Hofmann  by  the  dry  distillation  of  toluidine- 
lue  or  tritolylrosaniline,4  while  de  Laire,  Girard,  and  Chapoteau 
spared  it  by  heating  aniline  with  toluidine  hydrochloride  or 
>luidine  with  aniline  hydrochloride.     In  both  cases  the  product 
\  a  mixture  of  diphenylamine,  phenyltoluidine,  and  ditolylamine, 

cannot  be  readily  separated  by  fractional  distillation.5 
It  is  also  formed  when  equal  molecules  of  phenol  and  para- 
)luidine,  or  paracresol  and  aniline,  are  heated  with  an  excess  of 
inc  chloride  for  twenty  hours  to  260° — 3000.6     Phenylparatolui- 
line  crystallizes  readily  from  alcohol  in  long,  silky  needles,  melts 
it  87°  and  boils  at  334'5°.     Its  salts,  like  those  of  diphenyl- 
ie,  are  decomposed  by  water,  and  it  gives  a  fine  blue  colour- 
ion  with  concentrated  nitric  acid.     When  fused  with  mercuric 
ihloride  or  hexchlorethane,  a  splendid  violet  colouring  matter 
formed. 

1  Thomsen,  Ber.  Dcutsch.  Chem.  Ges.  x.  1582. 

2  See  also  Hiibner,  Tolleand  Athenstadt,  Ann.  Chem.  Pharm.  ccxxiv.  336. 

3  Morley  and  Abel,  ibid.  93,  313.  4  Ibid,  cxxxii.  291. 
6  Buch,  Ber.  Dcutsch.  Chem.  Ges.  xvii.  2634. 

6  Morley  and  Abel,  Ann.  Chem.  Pharm.  cxl.  347. 


66  AROMATIC  COMPOUNDS. 

Diparatolylamine,  (C6H4.CH3)2NH,  is  obtained  by  heating 
paratoluidine  with  its  hydrochloride  to  210° — 240°.  It  forms 
long  needles  melting  at  790,1  boils  at  355° — 360°,  and  is  coloured 
yellow  by  nitric  acid.  Its  salts  are  decomposed  by  water. 

Diparatolylnitrosamine,  (C6H4.CH3)2N(NO),  is  deposited  from 
petroleum-ether  in  golden-yellow,  hollow,  rhombic  crystals, 
melting  at  100° — 101°.  When  it  is  gradually  added  to 
well-cooled  fuming  nitric  acid,  hexnitrodiparatolylamine, 
(C6H(NO2)3CH3)2NH,  is  formed;  this  crystallizes  in  small 
yellow  pyramids  which  melt  at  258°,  and  are  slightly  soluble 
in  the  usual  solvents.2  - 

Acetparatoluide,  C6H4(CH3)N(C2H30)H,  was  first  observed 
by  Riche  and  Berard  in  the  preparation  of  aniline  oil  by  means 
of  iron  and  acetic  acid,  and  then  prepared  by  repeated 
distillation  of  paratoluidine  with  acetic  acid.3  Arndt  and 
Stadeler  obtained  it  in  the  same  way  from  crude  aniline,  and 
separated  it  from  the  acetanilide  formed  by  dissolving  the 
mixture  in  acetic  acid  and  precipitating  the  less  soluble  acet- 
toluide  with  water.4 

Acetparatoluide  is  dimorphous ;  on  the  gradual  evaporation  of 
its  alcoholic  solution  it  separates  in  monoclinic  crystals ;  when  a 
hot  solution  is  allowed  to  cool,  however,  it  crystallizes  in  rhombic 
needles.5  It  melts  at  147° 6,  and  boils  at  3070.7  1,000  parts  of 
water  dissolve  0'56  parts  at  65°,  and  0'886  parts  at  22°. 

Paratolyl  carbamide,  (C7H7)NH.CO.NH2.  Sell  prepared  this 
compound  by  the  action  of  potassium  cyanate  on  toluidine 
sulphate,8  and  Steiner  obtained  it,  together  with  ditolylguanidine, 
by  treating  fulminate  of  mercury  with  paratoluidine.9  It  is 
readily  soluble  in  hot  water,  and  crystallizes  in  thick  needles 
melting  at  1720.10 

Diparatolyl  carbamide,  (C7H7NH)2CO,  is  formed  on  the 
distillation  of  the  compound  just  described  (Sell),  or  when  it  is 
heated  to  150° — 170°  with  paratoluidine.11  It  is  also  obtained 
when  carbonyl  chloride  is  passed  into  a  solution  of  paratoluidine 
in  chloroform.12  It  is  insoluble  in  water,  and  crystallizes  from 

1  Ber.  Deutsch.  Chem.  Ges.  vi.  446. 

2  Cosack,  ibid.  xiii.  1092  ;  Lehne,  ibid.  xiii.  1544. 

3  Ann.  Chem.  Pharm.  cxxix.  77. 

*  Chem.  Centralbl.  1864,  707.  6  Panebianco,  Jahrcsber.  1878,  678. 

6  Hiibner,  and  Wallach,  Ann.  Chem.  Pharm.  cliv.  302. 

7  Beilstein  and  Kuhlberg,  ibid.  clvi.  74. 

8  Beilstein  and  Kuhlberg,  ibid,  cxxvi.  157. 

9  Ber.  Deutsch.  Chem.  Ges.  viii.  519.  10  Cosack,  ibid.  xii.  1450. 
11  Weith,  ibid.  ix.  821.  12  Michler,  ibid.  ix.  710 


PARATOLYL  URETHANE. 


67 


hot  alcohol  in  flat  needles,  which  resemble  those  of  benzoic  acid 
and  melt  at  256.° 

Paratolyl  urethane,  or  Ethyltolyl  carbamate,  (C7H7)NH(CO) 
(OC2H5),  is  obtained  by  the  action  of  chlorocarbonic  ether  on 
paratoluidine  in  ethereal  solution.  It  is  insoluble  in  water 
and  crystallizes  from  alcohol  in  long  prisms,  melting  at  52°. 

Paratolyl  carlimide,  CO.N.C7H7,  is  obtained  by  the  distillation 
>f  the  carbamic  ether  with  phosphorus  pentoxide,  as  a  strongly 
ifractive  liquid  boiling  at  185°;  its  vapour  possesses  a  penetrating 
odour  and  causes  a  flow  of  tears.1 

Paratolyl  thiocarlamide,  (C7H7)NH(CS)NH,  is  formed  when 
paratoluidine  hydrochloride  is  heated  with  ammonium  thio- 
cyanate,2  and  by  the  combination  of  paratolyl  mustard  oil  with 
ammonia.3  It  is  slightly  soluble  in  cold  water  and  crystallizes 
from  hot  alcohol  in  small  tablets  or  thick  needles  melting 
at  182°. 

Diparatolyl  thiocarbamide,  (C7H7.NH)2CS,  crystallizes  from  hot 
water  in  large,  pointed  prisms,  melting  at  1760.4 

Paratolyl  thiocarbimide,  or  Paratolyl  mustard  oil,  CS.N.C7H7. 
Hofmann  obtained  this  compound  by  heating  the  substance  just 
described  with  phosphorus  pentoxide.5  In  order  to  prepare  it, 
paratolyl  thiocarbamide  is  heated  to  160°  with  30  per  cent, 
sulphuric  acid.6  It  crystallizes  from  ether  in  long,  white  needles, 
lelts  at  26°,  and  boils  at  237°.  While  both  its  isomerides 
iss  the  characteristic  pungent  odo.ur  of  the  mustard  oils,  the 

lell  of  paratolyl  thiocarbimide  resembles  that  of  oil  of  aniseed. 

Like   other  thiocarbimides   it  combines  with  ammonia,  the 
imines,   and    the   aromatic    amido-bases    to    form    compound 

LO- ureas. 


HALOGEN  SUBSTITUTION   PRODUCTS 
OF  THE   TOLUIDINES. 

2050  A  very  large  number  of  these  has  been  prepared,  but 
only  the  mono-substitution  products  will  be  here  described. 


1  Hofmann,  Ber.  Deutsch.  Chem.  Ges.  iii.  656. 

2  Clermont  and  Wehrlin,  Bull.  Soc.  Chim.  xxvi.  126. 
8  Staats,  Ber.  Deutsch.  Chem,  Ges.  xiii.  136. 

*  Sell,  loc.  cit.  ;  Maly,  Jahrcsber.  1869,  637. 

6  Ber.  Deutsch.  Chem.  Ges.  i.  173. 

6  Liebermann  and  Natanson,  Li'Mg's  Ann.  ccvii.  160. 


68  AROMATIC  COMPOUNDS. 


CHLOROTOLUIDINES,  C6H3C1(CH3)NH2. 

Melting-  Boiling- 

CH3  :  NH2  :  Cl                                                              point.  point. 

1        2      4  small  plates1 29'5°  241° 

134  thin  plates 2 30°  230° 

143  liquid3 —  222° 

142  crystals4 26°  237°— 238'5 


BROMOTOLUIDINES,  C6H3Br(CH3)NH2. 

CH3  :  NH3  :  Br 

123  liquid  5 

1       24  plates6 32°  253°— 257° 

125  rhombohedra7 58°  240° 

134  prisms 8    .......  32° 

1       3      5       „         9 36°  255°— 260° 

1       3      6       „       10 78-5°  240° 

1       4      2       „        " 26° 

1       4      3       „        12 8°  240° 

Neville  and  Whither  have  also  prepared  dibromotoluidines 
together  with  higher  substitution-products,  by  methods  which 
giye  a  knowledge  of  their  constitutions.13 


IODOTOLUIDINES,  C6H3I(CH3)NH2. 

CH3  :  NH2  :  I 

124  needles14      .        .....       49° 

1        3      4  small  plates 15  .    ....      189°  — 

1  Beilstein  and  Kuhlberg,  Ann.  Chem.  Pharm.  clvi.  81 ;  clviii.  337. 

2  Gattermann  and  Kaiser,  Ber.  Deutsch.  Chem.  Ges.  xviii.  2599. 

3  Wroblevsky,  Ann.  Chem.  Pharm.  clxviii.  153  ;  Ber.  Deutsch.  Chem.  Ges.  vii. 
1062. 

4  Lellmann,  ibid.  xvii.  534. 

6  Neville  and  Winther,  ibid.  xiii.  1945. 

6  Korner,  Zeitschr.  Chem.  1869,  636  ;  Hiibner  and  Wallach,  Ann.  Chem.  Pharm. 
cliv.  298  ;  Heynemann,  ibid,  clviii.  340  ;  Hiibner  and  Roos,  Ber.  Deutsch.  Chem. 
Ges.  vi.  799. 

7  Wroblevsky  ;  Crete,  Ann.  Chem.  Pharm.  clxxvii   249. 

8  Neville  and  Winther,  Ber.  Deutsch.  Chem.  Ges.  xiii.  972. 

9  Wroblevsky,  Ann.  Chem.  Pharm.  cxcii.  192,  203  ;  Neville  and  Winther. 

10  Wroblevsky  ;  Neville  and  Winther. 

1  Neville  and  Winther,  Ber.  Deutsch.  Chem.  Ges.  xiv.  418. 

2  Wroblevsky,  Ann.  Chem.  Pharm.  clxviii.  153. 

13  Ber.  Deutsch.  Chem.  Ges.  xiv.  419.  14  Heynemann,  loc.  cit. 

15  Glassner,  ibid.  viii.  561. 


NITROTOLUIDINES.  69 


NITROTOLUIDINES,  C6H3(CH3)NH2(N02). 

2051  The  numbers  subjoined  refer  to  the  positions  of  the 
side-chains  in  the  order  given  in  the  formula. 

a-Orthonitro-orthotoluidine  (1:2:6)  is  formed  by  the  partial 
reduction  of  the  orthodinitrotoluene  melting  at  60°  —  61°.  It  is 
slightly  soluble  in  water,  more  readily  in  alcohol,  and  crystallizes 
in  long,  light  yellow  needles  melting  at  90°— 91°;  it  may 
be  converted  into  orthonitrotoluene  by  the  elimination  of  tht 
amido-group.1 

/3-Orthonitro-orthotoluidine  (1:2:3)  is  obtained  as  a  by^ 
product  in  the  preparation  of  the  compound  next  described,  and 
crystallizes  from  dilute  alcohol  in  orange-yellow  prisms,  united 
in  bushy  aggregates,  which  melt  at  97°.  It  is  converted  into 
metanitrotoluene  when  heated  with  a  solution  of  nitrogen 
trioxide.2 

Metanitro-orthotoluidine  (1:2:5)  is  obtained  by  the  nitration 
of  acetorthotoluide  and  decomposition  of  the  products  with  the 
calculated  quantity  of  alcoholic  potash.  It  is  readily  soluble  in 
alcohol,  but  only  very  slightly  in  boiling  water,  from  which  it 
crystallizes  in  small,  citron-yellow  needles,  melting  at  127°  — 128°. 
On  heating  with  an  alcoholic  solution  of  nitrogen  trioxide, 
metanitrotoluene  is  obtained,  while  when  the  amido-group  is 
replaced  by  bromine,  orthobromometanitrotoluene  is  formed, 
and  can  be  converted  into  orthobromotoluene  by  means  of  the 
diazo-reaction. 

Paranitro-ortJiotoluidine  (1:2:4).  When  the  phthalyl- 
toluide  obtained  by  heating  orthotoluidine  with  phthalic 
anhydride  is  nitrated,  two  mononitro-compounds  are  formed, 
one  of  which  occurs  only  in  small  quantities  and  on  decomposi- 
tion with  ammonia  yields  the  orthonitro-orthotoluidine  just 
described,  while  the  other  gives  paranitro-orthotoluidine,  which 
melts  at  109°,  and  may  be  converted  into  paranitrotoluene  by 
means  of  the  diazo-reaction  (Stadel).  It  is  also  formed  when 
orthotoluidine  is  dissolved  in  10  parts  of  sulphuric  acid  and  the 
well-cooled  solution  treated  with  the  calculated  quantity  of 
nitric  acid,  mixed  with  twice  its  weight  of  sulphuric  acid.  The 

1  Cunerth,  Ann.  Chem.  Pharm.  clxxii.  223  ;  Bernthsen,  Ber.  Deutsch.   Chem. 
Ges.  xv.  3016  ;  Stadel,  Ann.  Chem.  Pharm.  ccxxv.  384. 

2  Lellmann  and  Wiirthner,  ibid,  ccxxviii.   239. 
8  Beilstein  and  Kuhlberg,  ibid,  clviii.  345. 

236 


70  AROMATIC  COMPOUNDS. 

corresponding  nitracet-toluide  is  obtained  in  a  similar  manner 
by  dissolving  acetorthotoluide  in  20  parts  of  sulphuric  acid  ;  if} 
however,  only  4  parts  be  taken,  the  acetyl-compound  of  meta- 
nitro-orthotoluidine  is  also  formed.1 

a-Orthonitrometatoluidine  (1  :  3 :  2)  is  prepared  by  the  nitra- 
tion of  acetmetatoluide  and  decomposition  of  the  product  with 
alcoholic  potash.  It  crystallizes  in  fine,  saffron-yellow  needles 
melting  at  132°— 134°.  On  heating  with  an  alcoholic  solution 
of  nitrogen  trioxide,  it  is  converted  into  orthoiiitrotoluene 
(Beilstein  and  Kuhlberg). 

fi-Orthonitrometatoluidine  (1:5:2)  was  obtained  by  Limpricht 
from  the  corresponding  dinitrotoluene  (p.  71).  It  is  slightly, 
soluble  in  cold,  more  readily  in  hot  water,  and  readily  in  alcohol ; 
crystallizes  in  reddish  yellow  needles,  and  may  be  converted  into 
orthonitrotoluene  by  means  of  the  diazo-reaction.2 

Orthonitroparatoluidine  (1  : 4  :  2)  was  obtained  by  the  partial 
reduction  of  ordinary  dinitrotoluene.3  This  compound  alone  is 
formed  when  the  reduction  is  effected  with  ammonium  sulphide 
in  the  cold;  if,  however,  the  mixture  be  warmed,  paranitro- 
orthotoluidine  is  also  formed.4  Orthonitroparatoluidine  is  best 
prepared  by  dissolving  100  grams,  of  paratoluidine  in  2,000 
grams,  of  concentrated  sulphuric  acid,  and  gradually  adding  a 
mixture  of  75  grams,  of  concentrated  nitric  acid  with  300  grams, 
of  sulphuric  acid  to  the  solution  cooled  below  0°.  After  standing 
for  some  time,  the  liquid  is  poured  into  ice-water.5  It  crystal- 
lizes from  hot  water  in  broad,  yellow,  monoclinic  needles 
(Panebianco),  melting  at  77'5°,  and  may  be  converted  into 
orthonitrotoluene  by  means  of  the  diazo-reaction. 

Metanitroparatoluidine  (1:4: 3)  was  obtained  by  Beilstein 
and  Euhlberg  from  acetnitroparatoluide ;  the  latter  is  best 
prepared  by  dissolving  acetparatoluide  in  4  parts  of  sulphuric 
acid,  and  adding  the  calculated  amount  of  nitric  acid  mixed  with 
2  parts  of  sulphuric  acid  to  the  well-cooled  solution.  If  the 
amount  of  sulphuric  acid  be  increased,  the  acetyl-compound  of 
Orthonitroparatoluidine  is  also  formed,  while  metanitroparatolui- 
dine  can  be  obtained  by  the  direct  nitration  of  paratoluidine 
if  less  sulphuric  acid  be  used  (Nolting  and  Collin). 

1  Nolting  and  Collin,  Ber.  DeutscJi.  Chem.  Ges.  xvii.  261. 

2  Ibid,  xviii.  1401. 

3  Beilstein  and  Kuhlherg,  Ann.  Chem.  Pharm.  civ.  14. 

4  Limpricht,  Ber.  Deutsch.  Chcm.  Ges.  xviii.  1400  ;  Graeff,  Ann.  Chem.  Pharm. 
ccxxix.  340. 

6  Nolting  and  Collin,  loc.  cit. 


DINITROTOLUIDINES.  71 

It  is  readily  soluble  in  alcohol,  but  only  slightly  in  boiling 
water,  and  crystallizes  in  red  needles  or  prisms,  melting  at 
1160.1  On  heating  with  a  solution  of  ethyl  nitrite,  metanitro- 
toiuene  is  formed. 

Metanitroparamethyltoluidine,  C6H3(NO2)(GH3)NH(CH3),  is 
obtained  by  heating  nitrotoluidine  with  methyl  iodide  and 
wood-spirit ;  it  crystallizes  from  alcohol  in  red  needles,  and  from 
benzene  in  tablets  melting  at  84°  — 85°. 

Metanitropara-ethyltoluidine,  C6H3(NO2)(CH3)NH(C2H5),  forms 
large,  red  needles  melting  at  58° — 59°  (Gattermann). 


DINITROTOLUIDINES,  C6H2(CH3)(NO2)2NH2. 

2052.  a-Dinitro-orthotoluidine    (1:3:5:2)   is    formed    when 

linitro-orthocresyl  ethyl  ether  is  heated  with  alcoholic  ammonia. 

It  is  scarcely  soluble  in  boiling  alcohol,  slightly  in  toluene,  and 

crystallizes  in  prisms  or  tablets  which  exhibit  a  blue  iridescence 

and  melt  at  2080.2 

{3-Dinitrotoluidine  is  obtained  by  heating  ft- trinitrotoluene 
with  alcoholic  ammonia ;  it  crystallizes  from  glacial  acetic  acid 
in  short,  golden-yellow  needles,  melting  at  94°. 

y-Dinitrotoluidine  is  formed,  even  in  the  cold,  by  the  action  of 
alcoholic  ammonia  on  7- trinitrotoluene;  it  is  almost  insoluble  in  the 
ordinary  solvents  with  the  exception  of  hot  acetone  and  glacial 
acetic  acid,  and  forms  small,  hard,  golden-yellow  crystals  melting 
at  192°— 193°. 

Adjacent  Dinitroparatoluidine  (1:3:5:4)  is  formed  when 
acetparatoluide  is  brought  into  concentrated  nitric  acid  and  the 
product  treated  with  alcoholic  potash ; 3  it  may  also  be  obtained 
by  the  action  of  alcoholic  potash  on  dinitroparacresyl  ethyl 
ether.4  It  is  slightly  soluble  in  alcohol,  and  crystallizes  from 
carbon  disulphide  in  yellow  needles,  melting  at  1680.6  Chromic 
acid  oxidizes  it  to  chrysanisic  acid,  C6H2(CO2H)(NO2)2NH2. 

Symmetric  Dinitroparatoluidine  (1:2:6:4)  is  obtained  by 
the  reduction  of  a- trinitrotoluene  with  ammonium  sulphide ;  it 

1  Gattermann,  Ber.  Deutsch.  Chem.  Ges.  xviii.  1482 

2  Stadel,  ibid.  xiv.  900. 

3  Beilstein  and  Kuhlberg,  Ann.  Chem.  Pharm.  clviii.  341 ;  Kelbe,  Ber.  Deutsch. 
Chem   Ges.  viii.  877. 

4  Stadel,  loc.  cit.  5  Hiibner,  Ann.  Chem.  Pharm.  ccxxii.  74. 


72  AROMATIC  COMPOUNDS. 

crystallizes  from  acetic  acid  in  yellow,  hair-like  needles,  melting 
at  166'5° — 168°.  It  does  not  yield  chrysanisic  acid  on  oxidation, 
but  a  brown  powder  which  is  probably  an  azo-compound.1 

Thiotoluidine,  (CH3.C6H3.NH2)2S,  is  formed  when  paratolu- 
idine  is  heated  with  sulphur  and  litharge  to  140°.  It  crystallizes 
from  alcohol  in  lustrous,  odourless  plates  melting  at  103°,  and  is 
a  di-acid  base.  Its  salts  crystallize  well,  but  are  decomposed  by 
a  large  quantity  of  water.  When  the  solution  is  heated  with 
ferric  chloride  or  any  other  oxidizing  agent,  it  first  becomes 
yellow,  passing  into  brownish  red,  and  then  to  dull  red,  a  dark 
flocculent  precipitate  being  finally  formed.2 


DIAMIDOTOLUENES,   or  TOLYLENEDIAMINES, 

C6H3(CH3)(NH2)2. 

2053  a-Diamidotoluene,  or  ordinary  Metatoluylenediamine  (1:2:4) 
was  discovered  by  Hofmann  in  the  high  boiling  portions  of  crude 
aniline  oil,3  and  was  then  obtained  by  him  as  a  product  of  the 
reduction  of  ordinary  dinitrotoluene  with  iron  and  acetic  acid. 
It  is  best  prepared  by  the  reduction  of  dinitrotoluene  with  tin 
and  hydrochloric  acid.4  It  crystallizes  from  hot  water  in  l 
needles,  melts  at  99°,  and  boils  at  about  280°.  Its  aqueous 
solution  becomes  dark -coloured  in  the  air. 

a-Diamidotoluene  monohydrochloride,  C7H10N2.HC1,  is  obtained 
by  dissolving  the  base  in  the  calculated  amount  of  hydrochloric 
acid,  and  is  left  as  a  radiating  crystalline  mass  when  the 
solution  is  evaporated.5 

a-Diamidotoluene  dihydrochloride,  07H10N2(C1H)2,  crystallizes 
from  warm  hydrochloric  acid  in  needles. 

a-Diamidotoluene  sulphate,  C7HJON2.S04H2  +  2H20,  crystal- 
lizes from  water  in  long  prisms,  with  a  vitreous  lustre,  and  is 
precipitated  in  crystals  by  the  addition  of  alcohol  to  its  aqueous 
solution. 

fB-Diamidotoluene,  or  Orthotoluylenediamine  (1 :  3  : 4)  is  formed 
by  the  reduction  of  metanitroparatoluidine  with  tin  and  hydro- 

1  Beilstein,  Bcr.  Deutsch.  Chem.  Gcs.  xiii.  243. 
3  Merz  and  Weith,  ibid.  iv.  393. 

3  Jahresb.  Chem.  1861,  512  ;  Hell  and  Schoop,  Bcr.  Deutsch.  Chem.   Ges.  xii. 
723.  *  Beilstein,  Ann.  Chem.  Pharm.  cxxx.  242. 

5  Bernthsen,  Bcr.  Deutsch.  Chem.  Ges.  xi.  1759. 


DIAMIDOTOLUENES.  73 

chloric  acid.  It  forms  brilliant  white  scales,  which  are  tolerably 
stable  when  dry ;  its  aqueous  solution,  on  the  contrary,  rapidly 
becomes  coloured  black  in  the  air.  It  melts  at  88*5°,  and 
>ils  at  265°. 

When   a   crystal   is  thrown  into  water  it  takes  up  a  rapid 
)tatory  motion  in  dissolving,  as  do  the  other  diamines  (Pt.  III. 
238). 

f3-Diamidotoluene  hydrochloride,  C7H10N2(C1H)2,  crystallizes  in 
long,  very  soluble  needles. 

/3-Diamidotoluene  sulphate,  2(C7H10N2.S04H2)  +  3H20,is  more 
jadily  soluble  in  water  than  the  a-compound,  and  is  precipitated 
)y  alcohol  in  brilliant  white  scales,  with  a  nacreous  lustre.1 

Methyl  -  (3  -  diamidotoluene,  or  Metamidoparamethyltoluidine, 
C6H3(CH3)  (NH2)  NH  (CH3),  is  prepared  in  a  similar  manner 
to  the  following  compound,  and  crystallizes  in  four-sided  tablets, 
melting  at  43°— 44°. 

Ethyl-/3-diamidotoluene,    C6H3(CH3)(NH2)NH(C2H5),    is   ob- 
tined  by   the   reduction  of    metanitropara-ethyltoluidine,  and 
rstallizes  from  sulphuretted  hydrogen  water  in  large,  colourless 
iblets,  which  melt  at  54° — 55°,  and  soon  become  dark-coloured 
the  air.      The  peculiar   rotatory   motion    assumed    by   the 
ies  when  dissolving  in  water  was  first  observed  with  this 
>mpound.     A  crystal  which  is  not  too  heavy  acquires  such  a 
ipid  motion  that  it  appears  to  have  a  completely  closed  path, 
trace   of   fat  on  the  water  causes  cessation  of  the   motion 
(Gattermann). 

^/-Diamidotoluene,  or  Paratoluylenediamine  (1 :  3 :  5)  was  ob- 
dned  by  Beilstein  and  Kuhlberg  from  metanitro-orthotoluidine ; 
is  also   formed  when  ortho-amido-azotoluene   or   metamido- 
>toluene  is  reduced  with  tin  and  hydrochloric   acid.2     It  is 
lily  soluble  in  water,  crystallizes  from  hot  benzene  in  aggre- 
ttes  of  tablets,  melts  at   64°,  and  boils  at   273°— 274°.     On 
>xidation  with  manganese  dioxide  and  sulphuric  acid,  it  yields 
)luquinone. 

<y- Diamidotoluene  hydrochloride,  C7H10N2(HC1)2,  crystallizes 
from  hot  hydrochloric  acid  in  small  plates  with  a  nacreous 
lustre. 

^-Diamidotoluene  sulphate,  C7H10N2.S04H2,  is  slightly  soluble 
in  cold,  more  readily  in  hot  water,  and  is  precipitated  from  this 
solution  by  alcohol  as  a  white  powder. 

1  Beilstein  and  Kuhlberg,  Ann.  Chem.  Pharm.  clviii.  351. 

2  Nietzki,  Ber.  Deutsch.  Chem.  Ocs.  x.  832,  1158. 


74  AROMATIC  COMPOUNDS. 

As  already  mentioned,  solutions  of  its  salts  to  which  a  little 
orthotoluidine  has  been  added  are  coloured  a  deep  green  by 
ferric  chloride.  Nietzki  at  first  attributed  the  colouration  to 
paratoluylene-diamine  alone,  but  he  afterwards  found  that  the 
colour  was  only  produced  in  samples  prepared  from  ortho-amido- 
azotoluene,  which  had  not  been  completely  freed  from  ortho- 
toluidine ;  the  pure  compound  only  gives  the  reaction  after  the 
addition  of  the  latter  base. 

B-Diamidotoluene  (1  :  2 : 3)  is  formed  by  the  reduction  of  /3- 
orthonitro-orthotoluidine.  It  forms  red  crystals,  which  are 
readily  taken  up  by  the  usual  solvents,  smell  like  acetamide, 
melt  at  61P— 62°  and  boil  at  2550.1 


DIAZO-DERIVATIVES  OF  TOLUENE. 

2054.  Only  the  derivatives  of  paratoluidine  have  hitherto 
been  prepared  pure  ;  they  are  obtained  by  the  methods  used  in 
the  preparation  of  the  corresponding  benzene  derivatives.2 

The  diazo-compounds  of  the  two  other  toluidines  have  only 
been  obtained  as  intermediate  products  in  the  preparation  of 
derivatives ;  many  examples  of  this  kind  have  already  been 
given. 

Diazotoluene  nitrate,  CH3.C6H4N=nNO.N02,  crystallizes  in 
white  needles. 

Diazotoluene  sulphate,  CH3.C6H4N=N.O.SO2.OH,  forms  lus- 
trous needles  or  prisms. 

Diazo-amidotoluene,  CH3.C6H4N=N.NH.C6H4.CH3,  is  pre- 
pared by  passing  nitrogen  trioxide  into  a  solution  of  paratolu- 
idine in  a  mixture  of  alcohol  and  ether.3  It  crystallizes  in 
yellow  or  reddish  yellow  needles  or  prisms,  and  gives  a  platini- 
chloride  (C14H16N3)2PtCl6,  which  forms  yellow  tablets. 

Diazobenzene-amidotoluene,  C6H5N2.NH.C6H4.CH3,  was  ob- 
tained by  Griess  as  a  product  of  the  action  of  diazobenzene 
nitrate  on  paratoluidine,4  as  well  as  of  that  of  diazotoluene  nitrate 
on  aniline.5  It  crystallizes  in  narrow,  yellow  plates.  The 
formation  of  the  same  compound  by  two  different  reactions 

1  Lellmann  and  Wurthner,  Anti.  Chem.  Pharm.  ccxxviii.  243. 

2  Griess,  Jahresb.  Cficm.  1866,  458. 

3  Griess,  Ann.  Chem.  Pharm.  cxxi.  277 

4  Ibid,  cxxxvii.  60. 

6  £cr.  Deutsch.  Chem.  Ges.  vii.  1619. 


AZOTOLUENES.  75 


which  should  yield  isomeric  substances,  is  analogous  to  the  case 
of  diazobromobenzene-amidobenzene,  which  has  been  already 
discussed. 


HYDRAZINE-DERIVATIVES  OF  TOLUENE. 

2055  Paratolylhydrazine,  CH3.C6H4.NH=NH2,  is  prepared 
from  paratoluidine  just  as  is  phenylhydrazine  from  aniline. 
It  crystallizes  from  ethereal  solution  in  rhombic  tablets,  melts 
at  61°,  boils  with  slight  decomposition  between  240° — 244°,  and 
is  slightly  soluble  in  water,  but  readily  in  alcohol.1 

Diparatolylhydrazine,  (CH3.C6H4)2N=z:NH2,  is  formed  by  the 
action  of  zinc-dust  and  acetic  acid  on  diparatolylnitrosamine ; 
it  crystallizes  from  benzene  in  colourless  plates  melting  at  171° — 
172°,  and  is  a  weak  monacid  base.  Mercuric  oxide  converts  it 
into  diparatolylamine  without  the  formation  of  a  tetrazone-com- 
pound  (Pt.  III.  p.  29).2 


AZO-DERIVATIVES  OF  TOLUENE. 

2056  Azotoluenes,  CH3.C6H4N="NC6H4.CH3,  are  formed  by 
reduction  of  the  nitrotoluenes  or  oxidation  of  the  toluidines,  and 
are  converted  into  hydrazotoluenes,  C7H7.NH  —  NH.C7H7,  by 
further  reduction. 

Ortho-azotoluene  is  obtained  by  the  action  of  zinc-dust  and 
alcoholic  potash,  or  sodium  amalgam  and  alcohol  on  orthonitro- 
toluene,3  as  well  as  by  the  oxidation  of  orthotoluidine  with 
potassium  permanganate,  ammonia  and  oxalic  acid  being  simul- 
taneously formed.4  It  is  volatile  with  steam  and  crystallizes  from 
ether  in  red  prisms  melting  at  55°.  It  is  reduced  to  orthohydro- 
azotoluene  by  the  further  action  of  sodium  amalgam  ;  this  forms 
colourless  crystals  melting  at  165°,  which  decompose  at  a 
higher  temperature  into  orthotoluidine  and  ortho-azotoluene,  and 
are  readily  oxidized  to  the  latter  in  the  air. 

1  E.  Fischer,  Bcr.  Deutsch.  Chem.  Ges.  ix.  890. 

5  Lehne,  ibid.  xiii.  1546. 

1  Petriew,  Beilstein's  Org.  Chem.  976  ;  Ber.  Deutsch.  Chem.  Ges.  vi.  557. 
4  Hoogewerff  and  van  Dorp,  ibid.  xi.  1203. 


76  AROMATIC  COMPOUNDS. 

Meta-azotolucne  is  most  readily  formed  by  treating  metanitro- 
toluene  with  zinc-dust  and  alcoholic  potash.1  It  crystallizes  from 
weak  alcohol  in  orange-coloured  rhombic  prisms  melting  at  55°. 
When  it  is  heated  with  alcoholic  ammonium  sulphide,  the  liquid 
metahydrazotoluene  is  formed  and  rapidly  re-oxidizes  in  the  air. 

Para-azotoluene  may  be  best  obtained  by  dissolving  1  part  of 
paranitrotoluene  in  10  parts  of  alcohol  and  gradually  adding  22 
parts  of  4  per  cent,  sodium  amalgam  together  with  a  sufficient 
quantity  of  acetic  acid.2  The  oxidation  of  paratoluidine  with 
potassium  permanganate  affords  a  very  poor  yield  of  the  azo- 
compound,  but  better  results  may  be  obtained  by  oxidizing  the 
sulphate  of  the  base  with  potassium  ferricyanide  (Barsilowsky). 
It  is  also  formed  by  the  action  of  chromic  acid  on  a  solution  of 
paratoluidine  in  glacial  acetic  acid,3  and  by  that  of  bleaching 
.  powder  on  the  base  dissolved  in  chloroform.4 

It  is  slightly  soluble  in  alcohol,  readily  in  ether  and  petroleum- 
spirit,  crystallizing  from  the  latter  in  orange-yellow  needles 
which  melt  at  144°.  When  it  is  heated  to  100°  with  alcoholic 
ammonia  in  a  closed  vessel,  parahydrazotoluene  is  formed  and 
crystallizes  in  large  needles  or  tablets  which  melt  at  124°  and 
decompose  into  paratoluidine  and  parazotoluene  when  more 
strongly  heated.  It  rapidly  becomes  oxidized  to  the  latter  when 
its  alcoholic  solution  is  exposed  to  the  air  (Melms). 

Barsilowsky,  by  the  oxidation  of  paratoluidine  with  potassium 
ferricyanide,  obtained  parazotoluene  and  an  isomeric  substance,5 
which  Perkin  also  obtained  by  the  action  of  potassium  dichromate 
on  a  solution  of  toluidine  sulphate.6  It  forms  red,  hexagonal 
crystals  and  is  a  weak  base ;  Perkin  was  only  able  to  prepare  its 
platinichloride,  from  the  composition  of  which  he  concluded  that 
the  compound  was  a  triparatolylenediamine,  C21H21N3,  while 
Barsilowsky  found  that  it  is  reduced  by  alcoholic  ammonium 
sulphide  to  a  compound  isomeric  with  hydrazotoluene,  which 
crystallizes  in  small  colourless  plates  and  readily  oxidizes  in  the 
air.  It  is  a  weak  base  and  forms  a  very  characteristic  oxalate, 
(C14H16N2)2C2H2O4-hH2O,  which  separates  from  dilute  alcohol 
in  star-like  aggregates,  which  are  very  similar  to  the  seed 
feathers  of  the  dandelion. 

1  Barsilowsky,  Ann.  Chem.  Pharm.  ccvii.  114. 

2  Helms',  Ber.  Dcutsch.  Chem.  Gcs.  iii.  549. 

3  Perkin,  Journ.  Chem.  Soc.  1880,  i.  553. 

*  Schmitt,  Journ.  PraJct.  Chem.  [2]  xviii.  198. 

5  Ann.  Chem.  Pharm.  ccvii.  102. 

6  Journ.  Chem.  Soc.  1880,  i.  546. 


AMIDO-AZOTOLUENES.  77 

Klinger  and  Pitschke  have  now  found  that  the  red  substance 
is  an  amido-azo-compound  of  the  formula  CggH^N^1  It  is 
decomposed  into  paratoluidine  and  paraleucotoluidine,  C21H25N3, 
by  energetic  reduction  with  tin  and  hydrochloric  acid.  This 
compound  crystallizes  in  small  colourless  plates,  and  is  readily 
oxidized  topararosotoluidine,  C21H23N3,  which  forms  small  lustrous 
red  plates,  and  dissolves  in  water  with  an  intense  violet-red 
colour.  The  red  substance  has,  therefore,  the  following  con- 
stitution, C21H17(NH2)2N  =  N.C6H5.CH3.  These  compounds 
will  be  more  fully  described  in  the  sequel. 

Ortho-azoxytoluenefl^f^^f),  is  formed  when  orthonitrotoluene. 
is  heated  with  a  solution  of  sodium  in  methyl  alcohol,  and 
crystallizes  from  warm  petroleum-ether  in  yellow,  monoclinic 
needles  melting  at  59° — 60°.  It  is  not  converted  into  the 
isomeric  hydroxyazotoluene,  C7H7.N2.C7H6.OH,  on  heating 
with  concentrated  sulphuric  acid,  but  a  large  quantity  of  ortho- 
toluidine  is  formed,  the  oxygen  thus  liberated  producing  the 
oxidation  of  a  portion  of  the  ortho-azoxy toluene  to  a  mixture  of 
amorphous  acids. 

Klinger  and  Pitschke  consider  that  the  conversion  of  azoxy- 
benzene  into  hydroxyazobenzene  (Pt.  III.  p.  297)  is  brought 
about  in  a  similar  manner,  and  may  be  looked  upon  as  "  hy- 
droxylation  by  direct  oxidation."  2 

Amido  -  azotoluenes,  CH3.C6H4N  —  N.C6H3(CH3)NH2,  are 
formed  by  the  action  of  nitrous  acid  on  orthotoluidine  and 
metatoluidine,  while  paratoluidine,  as  already  mentioned,  is  thus 
converted  into  diazo-amidotoluene.  Compounds  belonging  to 
this  group  are  also  formed  by  the  action  of  a  diazoparatoluene 
salt  on  orthotoluidine  or  metatoluidine,  as  well  as  on  aniline, 
etc.3 

AmidortJio-azotoluene  is  obtained  by  passing  nitrogen  trioxide 
into  orthotoluidine  floating  on  a  saturated  solution  of  common  salt. 
The  product  is  allowed  to  stand  for  some  time,  washed  with 
water  to  remove  any  orthocresol  which  has  been  formed,  treated 
with  dilute  caustic  soda  and  finally  boiled  with  dilute  hydrochloric 
acid,  the  hydrochloride  thus  obtained  being  then  decomposed  by 
ammonia. 

Amidortho-azotoluene  is  slightly  soluble  in  water,  readily  in 
alcohol,  and  crystallizes  in  lustrous,  golden  plates  or  tablets, 


1  Ber.  Dcutsch.  Chem.  Ges.  xvii.  2439. 

*  Ibid,  xviii.  2551. 

3  Nietzki,  ibid.  x.  662,  832,  1156. 


78  AROMATIC  COMPOUNDS. 

melting  at  100°.  The  hydrochloride,  C14H15N3.C1H,  is  only 
slightly  soluble  in  water,  and  crystallizes  in  long,  thin  tablets 
with  a  silver  lustre. 

This  compound  is  decomposed  into  orthotoluidine  and  para- 
tolylenediamine  by  the  action  of  hydrochloric  acid  and  tin  or  zinc 
dust,  and  has  therefore  the  following  constitution : 


~CH3  ~CH3 

Amidometa-azotoluene  crystallizes  from  alcohol  in  broad, 
golden-yellow  needles  melting  at  80°.  The  hydrochloride  forms 
long,  dark  blue  needles,  which  are  only  slightly  soluble  in  hot 
alcohol,  and,  like  all  the  other  salts  of  this  class,  is  decomposed 
by  water.  On  reduction  with  tin  and  hydrochloric  acid,  para- 
tolylenediamine  is  formed. 

Ortho-amido2Jara-azotolnene  forms  yellow  tablets  melting  at  127° 
— 128°;  its  hydrochloride  crystallizes  in  cinnabar-red  needles, 
which  appear  of  a  steel-blue  colour  when  seen  by  reflected  light. 

Metamidoparazotoluene  crystallizes  from  alcohol  in  large,  yellow, 
plates,  melting  at  127°;  the  hydrochloride  forms  small,  steel-blue 
needles. 

Para-amidopara-azotoluene.  In  order  to  prepare  this  compound, 
the  isomeric  diazo-amidoparatoluene  is  heated  for  twelve  hours  to 
65°  with  five  times  its  weight  of  paratoluidine  and  one  equiva- 
lent of  paratoluidine  hydrochloride.  It  crystallizes  from  alcohol 
or  acetic  ether,  in  orange-red  lustrous  needles  melting  at  118'5°. 
Its  hydrochloride  crystallizes  in  light  yellow  needles  and  forms 
a  green  solution  in  water.  It  is  converted  into  paratoluidine 
and  orthotolylenediamine  by  reduction.1 

On  treatment  with  fuming  sulphuric  acid,  a  mixture  of  di- 
sulphonic  acids  is  formed,  which  comes  into  the  market  as 
"Acid  yellow  R,"  since  it  dyes  a  redder  shade  than  the  colouring 
matter  obtained  from  amido-azobenzene  (Part  III.  p.  307), 
which  is  therefore  called  "  Acid  yellow  G." 

a-Azoxytoluidine,  C14H12N2(NH2)2O,  is  formed  by  the  action 
of  sodium  amalgam  on  a  solution  of  orthonitroparatoluidine  in 
absolute  alcohol,  and  crystallizes  from  hot  water  in  small,  yellow 
needles  melting  at  148°.  It  is  a  diacid  base,  and  on  further 
reduction  yields  the  following  compounds  : 

1  Nolting  and  Witt,  Bcr.  Deutsch.  Chem.  Gcs.  xvii.  77. 


AZOXYTOLUIDINES.  79 

a-Azotoluidine,  or  Symmetric  a-diamido-azotoluene,  C14H12N2 
(NH2)2,  crystallizes  from  hot  water  in  red  needles  which  are 
readily  soluble  in  alcohol  and  melt  at  159°. 

a-Hydrazotoluidine,  C14H12(N2H2)(NH2)2,  is  almost  insoluble 
in  cold  water  and  alcohol,  but  is  slightly  soluble  in  hot  alcohol ; 
it  forms  small,  colourless,  rhombic  tablets  which  melt  at  180°. 
It  is  tolerably  stable  in  contact  with  cold  water  and  alcohol, 
but  rapidly  oxidizes  when  heated  with  them  in  the  air.1 

ft-Azoxytoluidine,  C14H12N2(NH2)2O,  is  obtained  from  para- 
nitro-orthotoluidine  and  crystallizes  in  long,  yellow  to  yellowish 
red,  silky  needles  melting  at  168°;  its  salts  crystallize  well. 
When  heated  with  concentrated  sulphuric  acid,  it  is  converted 
into  the  isomeric  hydroxyazo-compound,  just  as  is  the  case  with 
azoxybenzene  (Part  III.  p.  296) : 


N.C7H6.NH2  NC7H5(OH)NH2 

I  =     II 

N.C7H6.NH2  NC7H6.NH2. 


This  compound  crystallizes  from  alcohol  in  small,  dark  red 
needles,  which  melt  at  212°  with  decomposition.  Its  hydro- 
chloride  and  sulphate  are  only  slightly  soluble  in  water.  On 
treatment  with  stannous  chloride  and  hydrochloric  acid,  it 
is  resolved  into  ordinary  diamidotoluene  and  diamidocresol, 
C6H2(CH3)(NH2)2OH,  the  hydrochloride  of  which  crystallizes  in 
white  needles  which  become  coloured  blue  in  the  air ;  the  free 
base  immediately  becomes  resinous. 

@-Azotoluidine,  or  Symmetric  /3-diamido-azotoluene,  C14H12N2 
(NH2)2,  crystallizes  from  hot  water  in  small,  yellow  needles,  and 
is  deposited  on  the  gradual  evaporation  of  its  alcoholic  solution 
in  long,  red  needles,  which  melt  at  197°,  and  are  slightly  soluble 
in  water,  readily  in  alcohol.  The  sulphate  is  only  slightly 
soluble  in  water,  the  hydrochloride  being  somewhat  more  readily 
dissolved. 

(3-Hydrazotoluidine,  C14H12(N2H2)(NH2)2,  forms  yellow  needles 
which  rapidly  oxidize  when  exposed  to  the  air  in  a  moist  state. 
It  decomposes  without  melting  when  heated,  and  burns  with  a 
brilliant  flame.  It  is  almost  insoluble  in  absolute  alcohol,  but 
dissolves  readily  in  dilute  alcohol  and  water.2 


:xix.  340. 


kBuckney,  .ibid.  xi.  1451. 
Limpricht,  Ber.  Dcutsch.  Chem.  Ges.  xviii.  1403 ;  Graff,  Ann.  Chem.  Pharm. 


80  AROMATIC  COMPOUNDS. 

The  constitutions  of  the  two  azotoluidines  are  expressed  by 
the  following  formulae  : 


NH 


Metanitroparatoluidine  is  immediately  converted  by  sodium 
amalgam  into  the  corresponding  diamidotoluene,  while  metanitro- 
ortho-  and  a-orthonitrometa-toluidine  yield  resinous  products  on 
oxidation  (Limpricht). 

Asymmetric  diamido-azotoluene,  C7H7NnzNC7H6(NH2)2,  cor- 
responds to  chrysoidine  (Part  III.  p.  301)  and  is  formed  by  the 
action  of  diazotoluene  nitrate  on  a-diamidotoluene.  It  crystal- 
lizes from  alcohol  in  orange-yellow  needles  melting  at  183°.  Its 
hydrochloride,  (C14H16N4)C1H,  forms  red  needles.1 

2057  Tolusafranine,  C21H90N4.  The  history  of  this  dye,  which 
is  simply  known  as  "  safranine  "  in  commerce,  has  already  been 
briefly  indicated.  Phenosafranine  chloride,  the  lower  homologue 
of  tolusafranine,  has  been,  proved  2  to  have  the  following  con- 
stitution : 


NH2. 


This  formula  explains  all  the  facts  which  have  been  already 
given  (Part  III.  p.  369)  concerning  this  substance,  and  also  its 
formation  from  one  molecule  of  paradiamidobenzene  and  two 
molecules  of  aniline. 

Hofmann  and  Geyger  were  the  first  to  subject  the  com- 
mercial product  to  a  searching  examination ;  they  ascertained 

1  Hofmann,  Ann.  Chem.  Pharm.  x.  218. 

2  Witt,  Ber.  Deutsch.  Chem.  Ges.  xix.  3121.     Nietzki,  ibid.  3163. 


TOLUSAFRANINE.  81 


that  it  is  a  hydrochloride  of  the  formula  C21H21N4C1,  which 
is  not  attacked  by  alkalis,  but  is  readily  decomposed  by  moist 
silver  oxide,  and  that  it  is  not  a  derivative  of  aniline,  as  had 
been  up  to  that  time  assumed,  but  of  orthotoluidine,  from  which 
it  can  be  obtained  by  the  action  of  nitrous  acid  and  oxidation 
of  the  products  with  arsenic  or  chromic  acids.1  Witt  then 
found  that  it  is  formed  by  heating  amido-ortho-azotoluene  with 
orthotoluidine  hydrochloride,2  and  by  the  oxidation  of  a  mixture 
of  orthotoluidine  and  paratoluylenediamine.3  In  order  to  prepare 
it,  a  solution  of  equal  molecules  of  orthotoluidine  and  hydrochloric 
acid  is  treated  with  the  calculated  quantity  of  sodium  nitrate,  to 
obtain  amido-ortho-azotoluene  ;  the  product,  after  the  addition  of 
some  orthotoluidine  hydrochloride,  is  allowed  to  stand  and  is 
then  reduced  with  zinc-dust  and  hydrochloric  acid,  a  mixture  of 
fy-diamidotoluene  and  orthotoluidine  being  formed,  which  is  then 
neutralized  and  oxidized  with  potassium  dichromate ;  if  the 
solution  were  kept  acid,  toluquinone  would  be  formed.4  The 
safranine  is  then  precipitated  with  common  salt,  filtered  off, 
pressed,  dried  and  brought  into  the  market.5 

Tolusafranine  hydrochloride,  C21H21N4C1,  is  tolerably  soluble 
in  water  and  alcohol,  forming  red  solutions  which  possess  a 
characteristic  fluorescence ;  the  salt  is  precipitated  from  its 
aqueous  solution  by  the  addition  of  hydrochloric  acid  in  red 
crystals,  which  are  best  obtained  by  crystallizing  the  commercial 
product  from  boiling,  dilute  alcohol.  The  free  base,  obtained 
from  this  compound  by  means  of  silver  oxide,  probably  has  the 
formula  C21H21N4OH,  and  forms  reddish  brown  crystals  which 
take  a  faint  green  metallic  lustre  on  drying,  but  have  not  yet 
been  obtained  free  from  silver  chloride ;  they  are  soluble  in 
water  and  alcohol,  but  not  in  ether. 

Tohtsafranine  nitrate,  C21H21N4.NO3,  crystallizes  in  reddish 
brown  needles  which  are  only  very  slightly  soluble  in  cold 
water. 

Tolusafranine  picrate,  C21H20N4.C6H3(NO2)3O,  is  obtained  by 
the  addition  of  picric  acid  to  a  solution  of  one  of  the  salts  of 
the  base,  and  forms  brownish  red  needles,  insoluble  in  water, 
alcohol  and  ether. 


1  Bar.  Deutsch.  Chem.  Ges.  v.  526. 

2  Ibid.  x.  874. 

3  Ibid.  xii.  939  ;  Bindschedler,  ibid.  xiii.  207. 

4  Nolting,  Schultz,  Steinkohlentheer,  1049. 

5  Ibid.  527. 


82  AROMATIC  COMPOUNDS. 

Tolusafranine  shows  all  the  characteristic  reactions  of  the 
safranines  (Part  III.  p.  323). 

It  is  employed  as  a  substitute  for  saffron  for  dyeing  silk  and 
cotton  mordanted  with  tannin. 

2058  Toluykne-blue,  C15H18N4.HC1  +  H2O,  is  formed  when  36 
rjrms.  of  nitrosodimethylaniline  hydrochloride,  and  24  grms.  of 
metatoluylenediamine,  each  dissolved  in  500  c.cm.  of  water  at 
30°,  are  mixed.  ;  evolution  of  heat  takes  place  and  a  deep  green 
colouration  is  produced.  If  the  solution  be  now  allowed  to  stand, 
flat,  lustrous  brown  prisms  separate  out,  but  gradually  fall  into  a 
fine  crystalline  powder.  These  readily  form  blue  solutions  in 
water,  alcohol  and  acetic  acid  ;  traces  of  free  mineral  acids  change 
the  colour  into  reddish  brown,  the  original  shade  being  restored 
by  alkalis.  The  base  is  precipitated  by  alkalis  from  its  solution 
as  a  resinous  mass  which  takes  a  cupreous  lustre  in  the  air. 

Toluylene-blue  is  converted  by  tin  and  hydrochloric  acid  into 
the  leuco-compound,  C15H20N4HC1,  which  is  a  deliquescent 
crystalline  substance  and  is  very  readily  re-oxidized. 

Toluylene-red,  C15H16N4,  is  formed,  together  with  the  leuco- 
compound,  when  toluylene-blue  is  boiled  with  water  for  15-20 
minutes.  Stannous  chloride  precipitates  the  colouring  matter 
as  a  double  tin  salt  in  crystals,  which  are  then  decomposed  by 
an  alkali. 

Toluylene-red  crystallizes  in  orange-red  needles  containing 
four  moleculQS  of  water,  which  they  lose  at  150°  —  160°.  The 
anhydrous  base  is  blood-red  and  only  slightly  soluble  in  alcohol  ; 
it  forms  rose-red  normal  salts,  which  are  stable  and  readily 
soluble  in  water,  while  its  acid  salts  are  coloured  blue  and  are 
decomposed  by  water. 

Toluylene-violet,  C14H14N4,  is  formed  by  warming  toluylene- 
blue  with  metatoluylenediamine  dissolved  in  dilute  acetic  acid 
for  twelve  hours  to  35°  —  40°,  the  leuco-base  of  the  blue  compound 
being  simultaneously  formed  : 


Toluylene-violet  forms  red  crystals  with  a  green  reflection 
and  is  even  less  soluble  than  toluylene-red  ;  its  solution  is  flesh- 
coloured  and  shows  a  remarkable  orange-yellow  fluorescence. 
Its  slightly  soluble  normal  salts  are  coloured  violet  and  crystal- 
lize well,  while  the  acid  salts  have  a  grass-green  colour. 


TOLUYLENE  COLOURS.  83 

Witt   gives  the   following   constitutional   formulae   for   these 
compounds  :  l 

Toluylene-blue.  Toluylene-red.  Toluylene-  violet. 

C.H, 


N(OH,), 


,N 


JJ 


C.HKH,  O.H  . 


PHOSPHORUS   DERIVATIVES   OF  TOLUENE. 

2059  Paratolylphosphorus  dichloride,  CH3.C6H4PC12,  is  obtained 
the  continued  heating  of  15  parts  of  toluene  with  200  parts 
of  phosphorus  trichloride  and  3  parts  of  aluminium  chloride, 
or  by  heating  mercury  paratolyl  with  phosphorus  trichloride  to 
180° — 1900.2  It  is  a  crystalline  mass,  which  fumes  slightly  in 
the  air,  melts  at  25°,  and  boils  at  245°. 

Paratolylphosphorus  tetrachloride,  CH3.C6H4PC14,  is  formed  by 
the  combination  of  the  compound  just  described  with  chlorine, 
and  crystallizes  from  benzene  in  pointed  prisms  melting  at  42°. 
When  heated  in  a  sealed  tube  to  200°,  it  decomposes  with 
formation  of  the  dichloride  and  parachlorobenzyl  chloride  : 

;H3.C6H4PC14  =  CH3.C6H4PC12 + CH2C1.C6H4C1 + PC13 + HC1. 

It  rapidly  deliquesces  in  the  air,  forming  paratolylphosphorus 

tchloride,  CH3.C6H4POC12,  which  is,  however,  best  obtained 
in  a  similar  manner  to  phenylphosphorus  oxychloride,  by  the 
action  of  sulphur  dioxide  on  the  tetrachloride.  It  is  a  thick 
liquid,  boiling  at  284°— 285°. 

Paratolyl  phosphenylous  acid,  CH3.C6H4P02H2,  is  formed  by 
the  action  of  water  on  the  dichloride.  It  is  slightly  soluble 
in  water  and  crystallizes  from  alcohol  in  tablets  melting  at 
104°— 105°. 

Paratolylphosphenilic  acid,  CH3.C6H4PO(OH)2,  is  obtained  by 
decomposing  the  tetrachloride  or  the  oxychloride  with  water.  It 
is  readily  soluble  in  alcohol  and  crystallizes  from  water  in  matted, 
woolly  needles  which  melt  at  181°.  It  is  decomposed  by  ignitioa 

1  Bcr.  Dcutsch.  Chcm.  Ges  xii.  931. 

2  Michaelis  and  Paneck,  Liebig's  Ann.  ccxii.  203. 


84  AROMATIC  COMPOUNDS. 

with  lime,  with  formation  of  toluene  and  calcium  phosphate. 
Potassium  permanganate  oxidizes  it  to parabenzoplwsplwnilw  acid, 
C02H.C6H4PO(OH)2,  which  will  be  described  under  benzoic  acid. 

Paratolylphosphine,  CH3.C6H4.PH2,  is  obtained  by  heating 
tolylphosphenylous  acid  in  an  atmosphere  of  carbon  dioxide.  It 
is  a  liquid  which  possesses  a  most  intense  smell,  inhalation  of  its 
vapour  producing  headache  and  bleeding  of  the  nose.  It  boils 
at  178°  and  solidities  at  a  lower  temperature  to  a  crystalline  mass 
which  melts  at  4°.  It  is  rapidly  oxidized  to  tolylphosphenylous 
acid  in  the  air.  It  combines  with  hydriodic  acid  to  form 
paratolylphosphonium  iodide,  CH3.C6H4.PH3I,  crystallizing  in 
broad,  lustrous  needles  which  deliquesce  in  the  air  and  sublime 
in  cubes  when  heated  to  340°  in  a  current  of  carbon  dioxide. 

Dimethylparatolyl  phospliine,  CH3.C6H4.P(CH3)2,  is  obtained 
by  the  action  of  zinc  methyl  on  the  dichloride,  and  is  a  liquid 
which  has  an  unpleasant  smell,  boils  at  210°,  dissolves  in  acids 
and  is  not  oxidized  by  exposure  to  the  air.  Mercuric  oxide  con- 
verts it  into  dimethyltolylphosphine  oxide,  CH3.C6H4.P(CH3)20) 
which  is  a  thick  liquid.  The  phosphine  combines  with  methyl 
iodide  to  form  CH3.C6H4P(CH3)I,  crystallizing  in  needles  which 
melt  at  225°  and  yield  a  strongly  alkaline,  deliquescent 
hydroxide.1  The  corresponding  chloride  is  a  very  hygroscopic 
crystalline  body.2 

Orthotolylphosphorus  dichloride,  CH3.C6H4PC12,  is  obtained  by 
heating  orthomercury  tolyl  with  phosphorus  trichloride.  It  is 
a  liquid  which  boils  at  244°  and  does  not  solidify  even  at  -20°. 
It  combines  with  chlorine  forming  the  tetrachloride  as  a  solid 
yellow  mass.  It  is  decomposed  by  water  with  formation  of 
orthotolylpkosphenylous  acid,  which  is  a  liquid  but  forms  crystal- 
line salts,  while  the  orthotolylphosphenilic  acid  obtained  from  the 
tetrachloride  consists  of  small  crystalline  grains  which  melt  at 
141°  (Michaelis  and  Paneck). 

ARSENIC    DERIVATIVES    OF    TOLUENE. 

2060  Arsenparatolyl  chloride,  CH3.C6H4AsCl2,  is  obtained  by 
heating  mercury  paratolyl  with  arsenic  trichloride.3  It  crystal- 
lizes in  tablets,  melts  at  31°,  and  boils  in  an  atmosphere  of  carbon 
dioxide  at  2 6  7°  without  decomposition.  It  combines  with  chlorine 

1  Czimatis,  Bcr.  Dcutsch.  Chem.  Ges.  xv.  2014. 

2  Ibid.  2018. 

3  Michaelis  and  La  Coste,  Ann.  Chem.  Pharm,  cci.  246. 


ARSENIC  DERIVATIVES  OF  TOLUENE.  85 

forming  the  tetrachloride,  a  yellow  crystalline  mass,  which  is 
semi-fluid  at  the  ordinary  temperature  but  solidifies  completely 
on  cooling.  It  is  converted  by  water  into  tolylarsenic  add, 
CH3.C6H4AsO(OH)2,  which  crystallizes  in  long,  thin  needles. 
When  the  dichloride  is  boiled  with  caustic  soda  solution,  arsen- 
tolyl  oxide,  CH3.C6H4AsO,  is  formed  as  a  powder  melting  at 
156°. 

Arsendiparatolyl  chloride,  (CH3.C6H4)2AsCl,  is  formed  when 
mercury  tolyl  is  boiled  for  a  long  time  with  three  or  four  times  its 
amount  of  arsentolyl  chloride.1  It  is  an  oily,  yellow  liquid  which 
is  converted  by  boiling  alcoholic  potash  into  arsenditolyl  oxide 
((CH3.C6H4)2As)20,  which  crystallizes  from  ether  in  silky  needles 
melting  at  98°.  The  monochloride  combines  with  chlorine  to 
form  arsendiparatolyl  trichloride,  (CH3.C6H4)2AsCl3,  a  yellow 
powder  which  is  immediately  converted  by  water  into  dipara- 
tolylarsenic  acid,  (C7H7)2AsO(OH),  a  white  crystalline  mass 
which  is  slightly  soluble  in  water,  readily  in  alcohol,  from  which 
it  crystallizes  in  granules  melting  at  167°.  It  is  oxidized 
by  an  alkaline  solution  of  potassium  permanganate  to  dibenzo- 
arsenic  acid,  (CO2H.C6H4)2As02H. 

Triparatolylarsine,  (CH3.C6H4)3As,  is  formed  by  heating 
arsenparatolyl  oxide  to  360° : 

3CH3.C6H4AsO  =  (CH3.C6H4)3As+ As203. 

It  separates  from  ethereal  solution  in  large  crystals  which 
melt  at  145°  and  only  volatilize  at  temperatures  above  360°. 
When  chlorine  is  passed  into  its  chloroform  solution,  arsentri- 
tolyl  dichloride,  (CH3.C6H4)2AsCl2,  is  formed  as  a  white  crystal- 
line mass  which  is  dissolved  almost  without  decomposition  by 
boiling  water. 

Tritolylarsine  is  oxidized  by  alkaline  potassium  permanganate 
solution  to  tribenzo-arsenic  acid,  (CO2H.C6H4)3As(OH)2,  which 
will  be  described  under  benzoic  acid. 

Arsenorthotolyl  chloride,  C6H3.C6H4AsCl2,  has  been  obtained 
from  mercury  orthotolyl  and  arsenic  trichloride,  and  is  a  faintly 
smelling  liquid  which  boils  at  264° — 265°  in  an  atmosphere  of 
carbon  dioxide  without  undergoing  decomposition.  It  combines 
with  chlorine  to  form  the  tetrachloride,  which  is  a  thick  honey- 
yellow  liquid.  When  the  dichloride  is  boiled  with  soda  solution, 
arsenorthotolyl  oxide,  CH3C6H4AsO,  is  formed  as  a  powder  which 

1  La  Coste,  ibid,  ccviii.  18. 
237 


86  AROMATIC  COMPOUNDS. 

is  readily  soluble  in  hot  water,  slightly  in   alkalis,  and  melts 
at  145°— 146°. 

Ortliotolylarsenic  acid,  CH3.C6H4As.O(OH)2,  is  obtained  by  the 
action  of  water  on  the  tetrachloride,  and  crystallizes  from  hot 
water  in  fine  needles,  which  melt  at  159° — 160°  and  are  con- 
verted by  prolonged  heating  into  the  crystalline  anhydride, 
arsenorlhotolyl  dioxide,  CH3.C6H4AsO2  (La  Coste  and  Michaelis). 


ANTIMONY  DERIVATIVES  OF  TOLUENE. 

2061  These  compounds  are  obtained  by  the  action  of  sodium 
on  a  mixture  of  antimony  trichloride  with  bromotoluene 
dissolved  in  benzene.1  . 

Paratolylstibine,  Sb(C6H4.CH3)3,  is  readily  soluble  in  benzene, 
slightly  in  alcohol,  and  crystallizes  in  large,  transparent,  lustrous 
tablets  melting  at  127*5°.  It  forms  compounds  with  the 
elements  of  the  chlorine  group,  which  crystallize  from  benzene 
in  lustrous  prisms. 

Melting-point. 

Paratolylstibine  chloride,  Sb(C7H7)3Cl2  .  .  156-5° 
Paratolylstibine  bromide,  Sb(C7H7)3Br2  .  .  233'5° 
Paratolylstibine  iodide,  Sb(C7H7)3I2  .  .  182'5° 


Paratolylstibine  oxide,  Sb(C7H7)30,  is  obtained  by  treating  the 
bromide  with  alcoholic  potash  and  washing  the  residue  with 
water ;  it  is  slightly  soluble  in  benzene,  from  which  it  crystallizes 
in  small  needles  melting  at  223*5°.  If  it  be  dissolved  in  hot 
glacial  acetic  acid  and  treated  with  sufficient  water  to  produce 
turbidity,  fine,  transparent  crystals  of  paratolylstibine  hydroxide, 
Sb(C7H7)3(OH)2,  are  deposited  on  cooling  ;  this  compound  melts 
at  169*5°. 

Metatolylstibine,  Sb(C6H4.CH3)3,  forms  large  tablets  melting  at 
64*5° ;  the  bromide,  which  melts  at  113°  and  crystallizes  well,  is 
much  more  readily  soluble  in  ether  than  its  isomerides. 

Orthotolylstibine  is  a  thick  liquid,  and  forms  a  crystalline 
bromide.2 

3  Michaelis  and  Genzken,  Ber.  Deutsch.  Chem.  Ges.  xvii.  924. 
2  Ibid. 


MERCURY  DERIVATIVES  OF  TOLUENE.  87 


BORON    AND  SILICON  DERIVATIVES  OF 
TOLUENE. 

2062  Paratolylboron  chloride,  CH3.C6H4BCL>,  is  obtained  by 

i    the  action  of  boron  chloride  on   mercury  paratolyl,  and  is   a 

'    colourless  crystalline  mass,  which  melts  at  27°.     Water  converts 

it   into    tolylboric   acid,   CH3.C6H4B(OH)2,   a   violent    reaction 

taking  place ;  this  compound  crystallizes  from  hot  water  in  fine 

needles  melting  at  2400.1 

Paratolyhilicon  chloride,  CH3.C6H4SiCl3,  is  obtained  by  heating 
mercury  tolyl  with  silicon  tetrachloride  to  300° — 320°.  It  is  a 
strongly  refractive  liquid  which  boils  at  218° — 220°,  fumes  in 
the  air  and  is  converted  by  dilute  ammonia  into  paratolyl  silicic 
acid,  CH3.C6H4SiO(OH),  which  separates  from  ether  as  an  oil 
which  gradually  changes  into  a  thick,  elastic  mass.  It  commences 
to  lose  water  at  100°  and  is  completely  converted  at  200°  into 
paratolylsilicon  oxide,  which  is  a  solid  mass.2 

Silicon  paratolyl,  Si(C6H4.CH3)4,  is  readily  obtained  by  the 
action  of  sodium  on  a  mixture  of  silicon  chloride  and  parabromo- 
toluene.  It  separates  from  benzene  in  transparent  crystals 
melting  at  228°,  and  boils  above  360°  without  decomposition.3 

Dichlorosilicon  orthoditoluide,  SiCl2(NH.C7H7)2,  is  formed  by 
the  action  of  silicon  tetrachloride  on  orthotoluidine.  It  forms  a 
colourless,  amorphous  mass  which  readily  absorbs  moisture  with 
formation  of  silica  and  toluidine  hydrochloride.  Hydrochloric 
acid  gas  decomposes  it  into  toluidine  hydrochloride  and  silicon 
tetrachloride.4 


MERCURY  DERIVATIVES  OF  TOLUENE. 

2063  Dreher  and  Otto  obtained  mercury  paratolyl  by  the 
action  of  sodium  amalgam  on  the  bromotoluene  obtained  by  the 
direct  bromination  of  toluene.5  Ladenburg  then  showed  that 
the  ortho-compound  is  also  formed  in  this  way  and  can  readily  be 

1  Michaelis  and  Becker,  ibid.  xv.  185. 

2  Ladenburg,  Ann.  Chem.  Pharm.  clxxiii.   162. 
1  Polis,  Ber.  Deutsch.  Chem.  Ges.  xviii.  1542. 

4  Harden,  Journ.  Chem.  Soc.  1887,  44.  6  Ann.  Chem.  Pharm.  cliv.  171 


88  AROMATIC  COMPOUNDS. 

separated  from  the  para-compound  by  re-crystallization  from 
benzene.1  In  order  to  prepare  it,  bromotoluene  to  which  a  little 
acetic  ether  and  petroleum  have  been  added,  is  boiled  with 
1 '5  per  cent,  sodium  amalgam  for  a  longtime  in  an  apparatus 
connected  with  an  inverted  condenser,  and  the  products  separated 
by  re-crystallization  from  hot  benzene.2 

Mercury  orthotolyl,  (CH3C6H4)2Hg,  is  more  readily  soluble 
in  benzene  than  the  para-compound  and  crystallizes  in  large 
triclinic  tablets  melting  at  107°. 

Mercury  paratolyl  forms  matted  needles  which  melt  at  238° 
and  can  be  distilled  without  decomposition,  if  the  heating  be 
very  carefully  performed.  It  is  only  slightly  soluble  in  cold 
water.  Its  derivatives  resemble  those  of  mercury  phenyl. 

1  Ann.  Chem.  Pharm.  clxxiii.  162.  2  Ibid.  cci.  246 


BENZYL  GROUP. 

2064  The  compounds  obtained  by  the  replacement  of  one 
atom  of  hydrogen  in  the  methyl  group  of  toluene  by  other 
elements  or  radicals  are  looked  upon  as  derivatives  of  a  mono- 
valent  radical  phenylmethyl  or  benzyl,  C6H5.CH2. 


BENZYL  ALCOHOL,  C6H5.CH2.OH. 

Liebig  and  Wohler,  in  1832,  observed  that  when  oil  of  bitter 
almonds,  C7H60,  is  treated  with  alcoholic  potash  in  absence  of  air, 
benzoic  acid,  C7H6O2,  is  formed,  together  with  an  oily  substance, 
which  is  different  from  the  original  oil ;  they  make  the  following 
remarks  :  "  Although  we  have  not  investigated  this  new  product 
more  carefully,  there  can  be  no  doubt,  provided  that  the  alcohol 
takes  no  essential  part  in  the  reaction,  that  it  is  formed  either  by 
separation  of  oxygen  from  the  oil  of  bitter  almonds  or  by  some 
reaction  involving  the  sharing  of  the  elements  of  water.  In  the 
former  case  its  composition  will  be  expressed  by  the  formula 
C14H120,  in  the  latter  by  C14HU02 "  *  (C  =  6,  O  =  8). 

Cannizzaro  then  found  that  this  substance  is  "  the  alcohol 
corresponding  to  benzoic  acid,"  and  that  although  its  composition 
does  not  correspond  with  that  of  the  ordinary  alcohols,  it  behaves 
towards  reagents  as  an  alcohol,  the  aldehyde  of  which  would  be  oil 
of  bitter  almonds.  He  obtained  the  latter  compound  by  oxidizing 
the  alcohol  with  ordinary  nitric  acid,  while  chromic  acid  gave 
benzoic  acid.  He  further  showed  that  the  action  of  hydrochloric 
acid  produced  an  ethereal  chlorine  compound,  C7H7C1,  which  is 
derived  from  the  alcohol  of  benzoic  acid  and  is  reconverted  into 
the  alcohol  by  treatment  with  caustic  potash ;  when  heated  with 
alcoholic  ammonia  it  yielded  a  base  which  differed  essentially 

1  Ann.  Chem.  Pharm.  iii.  254,  261. 


90  AROMATIC  COMPOUNDS. 

from  toluidine.  He  also  prepared  the  acetate,  which  is  decom- 
posed by  warming  with  caustic  potash  into  acetic  acid  and  the 
alcohol  of  benzoic  acid,  and  says  :  "  This  kind  of  alcohol  appears 
to  be  the  type  of  a  whole  class  of  new  alcohols,  the  more  complete 
investigation  of  which  is  now  in  progress."  l 

In  the  course  of  this  investigation  he  found  that  concentrated 
alcoholic  potash  produced  a  decomposition  in  which  benzoic  acid 
and  toluene  were  formed  from  the  alcohol,  so  that  the  latter 
stands  in  the  same  relation  to  toluene  as  wood-spirit  to  marsh 
gas:2 

C7H80  +  KOH  =  C7H5KO2  +  2H2 

C7H80  +  H2  =  C7H8  +  H20. 

He  also  succeeded  in  converting  toluene  into  the  alcohol ;  by 
the  action  of  chlorine  on  the  boiling  hydrocarbon  he  obtained 
chlorobenzyl,  which  was  identical  with  that  obtained  by  the 
action  of  hydrochloric  acid  on  the  alcohol.  On  heating  with 
potassium  acetate,  both  compounds  gave  benzyl  acetate,  which 
yielded  the  alcohol  on  saponification  with  caustic  potash.3 

This  compound  had  previously  been  in  the  hands  of  several 
chemists,  who  had  not,  however,  recognised  its  nature.  Fremy 
isolated  from  Peru  balsam  a  compound  which  he  named  cinnamem, 
from  which  he  obtained  cinnamic  acid  and  peruvin,  C9H12O,  by 
heating  with  caustic  potash.4  The  latter  compound,  according 
to  Plantamour,  who  prepared  it  the  same  way  and  also  observed 
the  formation  of  cinnamic  acid,  is  ethyl  cinnamate ;  he  was  led 
to  this  conclusion  by  the  fact  that  when  he  heated  it  with 
caustic  potash  and  evaporated  the  whole  to  dryness,  he  obtained 
potassium  cinnamate  and  a  combustible  vapour  which  he  took 
for  ethyl  alcohol.  He  remarks  that  the  origin  of  this  substance, 
•which  was  only  recognised  in  this  indirect  and  remarkable 
manner,  still  requires  explanation.5  Scharling  first  accurately 
determined  the  composition  of  cinnamein  and  looked  upon  it  as 
a  compound  ether.  The  peruvin,  C7H8O,  obtained  from  it  he 
considered  as  an  alcohol,  probably  identical  with  Cannizzaro's 
compound.  When  he  brought  it  into  contact  with  platinum 
black,  the  smell  of  oil  of  bitter  almonds  was  produced.6 

Strecker  then  expressed  his  conviction  that  cinnamein  is  the 
cinnamic  ether  of  benzyl  alcohol,7  and  was  confirmed  by  Kraut, 

1  Ann.  Chem.  Pharm.  Ixxxviii.  129.  2  Ibid.  xc.  252. 

8  Ibid  xcvi.  246.  4  Ibid.  xxx.  324. 

8  Ibid.  xxx.  341.  «  Ibid,  xcvii.  168. 

1  Lehrb.  Org.  Chem.  1856,  456. 


BENZYL  COMPOUNDS.  91 

. 

according  to  whom  Fremy's  peruvin  was  a  mixture  of  this 
alcohol  and  toluene,  Plantamour's  compound  being,  however, 
the  pure  alcohol.  The  acid  taken  for  cinnamic  acid  was 
obviously  benzoic  acid  and  the  combustible  vapour  consisted  of 
toluene.1 

The  liquid  portion  of  Peru  balsam2  consists  chiefly  of  the 
benzoate  and  cinnamate  of  benzyl,  but  also  contains  some  free 
benzyl  alcohol.3  Both  ethereal  salts  occur  in  Tolu  balsam,4  and 
the  latter  in  liquid  styrax.5 

Benzyl  alcohol  also  seems  to  be  contained  in  the  oil  of  the 
cherry-laurel,  which  consists  chiefly  of  benzaldehyde  and  its 
cyanhydrin  (Tilden).6 

The  action  of  alcoholic  potash  on  oil  of  bitter  almonds,  which 
was  observed  by  Cannizzaro,  is  characteristic  of  the  aromatic 
aldehydes,  oxidation  and  reduction  taking  place  simultaneously : 

C6H5.CHO  +  KOH  =  C6H5.CO.OK  +  H2 
C6H5.CHO  +  H2  =  C6H5.CH2.OH. 

Benzyl  alcohol  is  also  formed  by  the  action  of  sodium  amalgam 
and  water  on  benzaldehyde7  and  on  benzoic  acid,8  while  the 
fatty  acids  are  not  changed  by  nascent  hydrogen.  Benzoyl 
chloride,  C6H5.COC1,  is  also  reduced  to  benzyl  alcohol  by  the 
action  of  sodium  amalgam  and  hydrochloric  acid,9  while  a  better 
yield  may  be  obtained  by  adding  sodium  amalgam  to  an  ethereal 
solution  of  benzamide,  C6H5.CONH2,  which  contains  water  and 
has  been  rendered  faintly  acid  with  hydrochloric  acid.10 

1  Ann.  Chem.  Pharm.  cvii.  208. 

2  Peru  balsam,  like  Tolu  balsam,  was  first  described  by  the  Spanish  physician 
Monardes  (p.  3)  ;  the  latter  is  derived  from  Myroxylon  toluifera,  the  former  from 
Myroxylon  pareirae,   a  native  of  Central  America  in  the  district  of  Costa  del 
Balsamo.    Peru  balsam  contains  the  same  substances  as  that  from  Tolu,  together 
with  several  of  a  different  nature,  this  being  due  to  the  difference  in  the  methods  of 
extraction  employed  in  the  two  cases.     While  the  latter  is  obtained  by  the  simple 
process  of  making  incisions,  it  is  necessary  to  remove  the  bark  before  extracting  the 
Peru  balsam.  In  order  to  accomplish  this,  it  is  first  loosened  by  blows  of  a  hammer 
or  the  back  of  an  axe,  and  is  then  superficially  charred  by  burning  torches  or 
bundles  of  twigs,  the  effect  of  this  treatment  being  either  to  detach  it  or  to  render 
its  removal  a  matter  of  no  difficulty.     The  stem  is  next  wrapped  round  with  rags, 
which  become  saturated  with  the  balsam,  and  are  then  removed  and  heated  with 
water  ;  the  balsam  is  thus  separated  from  the  cloth  and  sinks  to  the  bottom  of  the 
vessel  (Fliickiger  and  Hanbury,  Pharmacographia,  2  Ed.  p.  205). 

3  Kraut,  Ann.  Chem.  Pharm.  clii.  131. 

4  Ber.  Deutsch.  Chem.  Ges.  ix.  830. 

8  Laubenheimer,  Ann.  Chem.  Pharm.  clxiv.  289. 

6  Pharm.  Journ.  Trans.  [3]  v.  761. 

7  Friedel,  Ann.  Chem.  Pharm.  cxxiv.  324. 

8  Herrmann,  ibid,  cxxxii.  75.  9  Lippmann,  ibid,  cxxxvii.  252. 
10  Guareschi,  Gazz.  Chim.  Ital.  iv.  465  ;  Ber.  Deutsch.  Chem.  Ges.  vii.  1462. 


92  AROMATIC  COMPOUNDS. 


It  is  best  obtained  from  benzyl  chloride,  which  can  readily  be 
prepared  from  toluene,  by  boiling  it  for  two  hours  with  water  and 
lead  hydroxide,1  or  by  simply  boiling  it  for  two  days  with 
25 — 30  parts  of  water,  76  per  cent,  of  the  theoretical  yield  being 
thus  obtained.2 

According  to  Mennier,  it  may  be  advantageously  prepared  by 
boiling  equal  parts  of  benzyl  chloride  and  potassium  carbonate 
with  10  parts  of  water  for  several  hours.3 

Cannizzaro's  process  does  not  serve  for  the  preparation  of  the 
alcohol  from  benzaldehyde,  as  the  action  of  the  alcoholic  potash 
is  only  gradual,  even  on  long  continued  heating,  and  a  consi- 
derable loss  is  experienced  through  the  formation  of  resinous 
products.  If,  however,  10  parts  of  the  aldehyde  be  shaken 
up  with  a  solution  of  9  parts  of  caustic  potash  in  6  parts  of 
water  until  a  permanent  emulsion  is  obtained,  and  sufficient 
water  to  form  a  clear  solution  be  then  added  to  the  semi-solid 
mass  of  crystals  formed  on  standing  by  the  separation  of  potas- 
sium benzoate,  the  benzyl  alcohol  can  readily  be  extracted  from 
the  liquid  with  ether.  The  ether  is  then  distilled  off  and  the 
residue  purified  by  rectification  without  being  dried.  In  this 
way  92  per  cent,  of  the  theoretical  yield  can  be  obtained,  while 
the  application  of  alcoholic  potash  only  gives  a  yield  of  43  per 
cent.  Since  only  one  half  of  the  benzaldehyde  is  converted  into 
the  alcohol,  benzyl  chloride  is  a  more  economical  source ;  it  is, 
however,  more  difficult  to  obtain  in  a  state  of  purity  than 
benzaldehyde  and  therefore  does  not  yield  a  pure  product  so 
readily.  As  mentioned  above,  it  is  impossible  to  dry  the 
alcohol  before  distillation;  it  combines  with  calcium  chloride 
slowly  in  the  cold,  more  rapidly  on  heating,  and  is  attacked  by 
solid  caustic  potash.4 

If  two  molecules  of  benzaldehyde  be  added  to  a  solution  of 
one  atom  of  sodium  in  12  parts  of  methyl  alcohol  and  the  mixture 
heated  in  an  apparatus  connected  with  inverted  condenser,  a  white 
substance  soon  separates  out,  which  seems  to  be  a  compound 
of  methyl  benzoate  and  sodium  methylate,  since  it  is  formed 
when  these  are  heated  together.  If  the  heating  be  continued 
for  about  two  days  and  the  mass  neutralized  with  glacial  acetic 
acid,  and  then  heated  with  water,  an  oil  separates  out  which  can 


1  Grimaux  and  Lauth,  Ann.  Chem.  Pharm.  cxliii.  80. 

2  Niederist,  ibid,  cxcvi.  353. 

3  Bull.  Soc.  Chim.  xxxviii.  159. 

4  B.  Meyer,  Ber.  Deutsch.  Chem.  Ges.  xix.  2394. 


BENZYL  ALCOHOL.  93 


be  separated  into  two  portions  by  distillation.  About  two-thirds 
of  the  whole  boil  between  198° — 210°,  and  consist  of  a  mix- 
ture of  equal  molecules  of  methyl  benzoate,  boiling  at  199°, 
and  benzyl  alcohol,  boiling  at  206°.  These  cannot  be  separated, 
but  if  the  benzoate  be  saponified,  pure  benzyl  alcohol  can 
readily  be  obtained. 

The  smaller  portion  of  the  product,  about  20 — 30  per  cent, 
on  the  benzaldehyde  employed,  boils  at  320° — 324°,  and  consists 
of  benzyl  benzoate.  This  is  polymeric  with  the  aldehyde  and  is 
formed  directly  from  it : 

C6^5-  CHO  C6H5.CH2x 

C6H5-CHO  C6H5.CO  > 

The  chief  reaction,  however,  consists  in  the  conversion  of  the 
benzaldehyde  in  the  presence  of  sodium  methylate  into  methyl 
benzoate  and  benzyl  alcohol : 

2C6H5.CHO  +  CH3.OH  =  C6H5.CO.OCH3  +  C6H5.CH2.OH. 

The  two  latter  appear  to  be  then  partially  converted  into 
benzyl  benzoate  and  methyl  alcohol.1 

If  this  reaction  be  employed  for  the  preparation  of  benzyl 
alcohol,  the  original  product  is  simply  saponified. 

In  order  to  prepare  it  from  Peru  balsam,  the  latter  is  thoroughly 
agitated  with  2  volumes  of  caustic  potash  of  sp.  gr.  1*2,  the 
emulsion  exhausted  with  ether,  the  extract  separated  and  eva- 

>rated,  and  the  residual  oil  heated  with  4  volumes  of  caustic 

)tash  of  sp.  gr.  1*3  until  a  homogeneous  liquid  is  obtained.  The 
>ulpy  mass  of  crystals  formed  on  cooling  is  pressed  in  linen, 
md  the  liquid  diluted  with  water  and  distilled  until  the  dis- 
illate  ceases  to  appear  milky.  The  alcohol  is  then  separated 

>m  the  aqueous  distillate  and  the  portion  which  remains  dis- 
)lved  in  the  latter  extracted  by  ether.2 

Properties. — Benzyl  alcohol  is  a  liquid  which  possesses  a  faint 
aromatic  odour,  boils  at  206°,  and  has  a  sp.  gr.  of  T063  at  0°. 
It  is  not  insoluble  in  water,  as  was  at  one  time  thought,  for 
100  parts  of  water  at  17°  dissolve  4  parts  (E.  Meyer).  When 
heated  with  hydriodic  acid  and  a  little  phosphorus  to  170°— 
180°,  it  is  almost  completely  reduced  to  toluene,  only  a  small 

1  L.  Claisen,  private  communication. 

2  Kachler,  Ber.  Deutach.  Chem.  Ges.  ii.  512. 


94  AROMATIC  COMPOUNDS. 

amount  of  higher  boiling  substances  being  formed.1  Its  other 
characteristic  properties  which  were  ascertained  by  Cannizzaro 
have  been  already  mentioned. 


BENZYL   ETHERS. 

2065  Benzyl  methyl  ether,  C6H5.CH2.O.CH3,  was  obtained  by 
Sintenis  by  heating  benzyl  chloride  with  methyl  alcohol  and 
caustic  potash.2  It  is  a  pleasant  smelling  liquid,  which  boils 
at  167° — 168°  and  is  decomposed  by  chlorine  in  the  cold  with 
formation  of  benzaldehyde  and  methyl  chloride  : 

C6H5.CH2.O.CH3 + C12  =  C6H5.COH  +  CH3C1  +  HC1. 

Benzyl  ethyl  ether,  C6H5.CH2.O.C2H5,  is  formed  when  benzyl 
.chloride  is  boiled  with  alcoholic  potash,  and  is  a  mobile  liquid, 
possessing  a  pleasant  odour  and  boiling  at  182° — 1840.3  Chlorine 
acts  upon  it  in  the  cold  just  as  on  the  methyl  ether ;  at  the 
boiling  point,  however,  benzoyl  chloride  is  formed : 

C6H5.CH2.O.C2H5  +  2C12  =  C6H5.COC1  +  C2H5C1  +  2HC1. 

In  the  presence  of  iodine,  ethyl  iodide  and  parachlorobenz- 
aldehyde,  C6H4C1.COH,  are  obtained  (Sintenis). 

Bromine  produces  a  similar  decomposition,  benzaldehyde,  ethyl 
bromide  and  hydrobromic  acid  being  first  formed  ;  the  latter 
then  decomposes  another  portion  of  the  ether  into  benzyl 
bromide  and  ethyl  bromide,  and  the  benzaldehyde  is  converted 
into  benzoyl  bromide  by  the  excess  of  bromine.4 

Dibenzyl  ether  or  Benzyl  oxide,  (C6H5.CH2)2O.  Cannizzaro 
obtained  this  compound  by  heating  benzyl  alcohol  to  120° — 125° 
with  boron  trioxide  and  treating  the  product  with  water  and 
potassium  carbonate.  When  the  dried  oil  is  distilled,  unaltered 
benzyl  alcohol  comes  over  first,  and  then  the  ether,  a  resinous 
hydrocarbon  remaining  behind  in  the  retort.  Dibenzyl  ether 
is  a  colourless,  oily  liquid,  which  boils  at  310° — 315°  and  has  a 
faint  indigo-blue  fluorescence.  It  decomposes  into  toluene  and 

1  Grabe,  Per.  Deutsch.  Chem.  Ges.  viii.  1054. 

2  Ann.  Chem.  Pharm.  clxi.  334. 
8  Cannizzaro,  Jahresb.  1856,  582. 

*  Paterno,  Gaz.  Chim.  Ital.  i.  586. 


BENZYL  ETHERS.  95 


benzaldehyde  when  heated  to  a  few  degrees  above  315°  in  a 
sealed  tube  ;  a  very  small  quantity  of  the  resinous  hydrocarbon  is 
also  formed  in  this  way.  Dibenzyl  ether  is  also  formed  in  small 
quantity,  together  with  various  hydrocarbons,  when  benzyl 
chloride  is  heated  with  water  to  1900.1 

C.  W.  Lowe  prepared  dibenzyl  ether  in  the  following  way : — 
Sodium  was  added  to  benzyl  alcohol  diluted  with  ether.  Towards 
the  end  of  the  reaction  heat  was  applied  in  order  to  convert  all 
the  alcohol  into  sodium  benzylate.  The  product  was  mixed  with 
benzyl  chloride  and  gently  heated,  when  a  rather  violent  reaction 
set  in. 

Dibenzyl  ether  is  a  perfectly  colourless  liquid,  having  a  slight 
but  persistent  odour  of  hawthorn  blossom.  Its  sp.  gr.  at  16°  is 
r0359.  It  boils  at  295° — 298°,  at  the  same  time  being  partially 
resolved  into  toluene  and  benzaldehyde.  This  decomposition 
goes  on  more  rapidly  at  315°  as  Cannizzaro  found,  a  very  small 
quantity  of  a  resinous  body  being  formed  at  the  same  time. 

Benzyl  phenyl  ether,  C6H5.CH2.O.C6H5,  is  obtained  by  heating 
benzyl  chloride  with  potassium  phenate  and  alcohol  to  1000.2 
It  forms  scaly  crystals  with  a  nacreous  lustre,  melts  at  38° — 39° 
and  boils  at  286°— 287°  (Sintenis).  On  heating  with  con- 
centrated hydrochloric  acid  to  100°,  it  decomposes  into  benzyl 
chloride  and  phenol ;  hydrobromic  acid  produces  a  similar 
decomposition.  Chlorine  attacks  it  in  the  cold  with  formation 
of  benzyl  chloride  and  substitution  products  of  phenol,  the 
action  of  bromine  being  quite  analogous.  In  the  presence  of 
mercuric  oxide,  on  the  other  hand,  substitution  products  of  the 
ether  are  formed  (Sintenis). 

Melting-        Boiling- 
point,  point. 

Benzyl  chloro-  )  CrH..CH.,  )  ~  , 
phenyl  ether    j     6C6H4C1  \  °  lonS  needles  70  ~71 

Benzyl  bromo-  j  C6H5X!H2  j  fe  59°-59'5°      - 

phenyl  ether  j  C6H4Br  j 
Benzyl  ortho-tCfiHCH2  j  d  _  285o_29()o 

cresyl  ether 3  y  CH3.C6H4  j 
Benzyl  para- |  C6H5.CH2  [Q  hexagonal  )  ,.0 

cresyl  ether    j  CH3.C6H4  )          prisms         } 

Ethers  of  benzyl  ivith  the  dihydroxylenzenes  are  formed  when 


1  Limpricht,  Ann.  Chem.  Phartn.  cxxxix.  307. 

2  Lauth  and  Grimaux,  ibid,  cxliii.  81. 

3  Stadel,  Bcr.  Deutsch.  Chem.  Ges.  xiv.  898. 


96  AROMATIC  COMPOUNDS. 

the    latter    are    heated    with    benzyl    bromide    and   alcoholic 
potash.1 

Melting- 
point. 

Benzylquinol,      C6H4  {  ^  j  large   lustrous  j 

4  ( O.CH2.C6H5  j          scales         j 

Dibenzylquinol,   C6H4(O.CH2.C6H5)2,  lustrous  tablets        130° 

Dibenzylresor-  1  p  TT  /n  prr  n  TT  N    J  small  lustrous  }        ,.,,0 
cinol,          j  C6H4(O.CH2.C6H5)2,  j        ^^       j       76 

Dibenzylcate-    |  C6H,(O.CH2.C6H6)2,  yellow  needles  61° 

CI1O1,  J 

ETHEREAL  SALTS  OF  BENZYL. 

2066  Benzyl  chloride,  C6H5.CH2C1.  Cannizzaro  obtained  this 
compound  by  the  action  of  hydrochloric  acid  on  benzyl  alcohol 
and  it  is  also  formed  by  that  of  chlorine  on  boiling  toluene.2 

It  is  prepared  on  the  large  scale  by  the  latter  method,  the 
toluene  being  contained  in  large  glass  balloons  heated  by  a  bath 
of  calcium  chloride,  and  the  chlorine  passed  through  in  such  a 
manner  that  it  chiefly  comes  in  contact  with  the  vapour  of  the 
toluene.  This  is  effected  by  only  allowing  the  leaden  conducting 
tube,  which  terminates  in  a  short  piece  of  glass  tubing,  to  dip  a 
small  distance  below  the  surface  of  the  boiling  liquid.  The 
vapours  of  toluene  are  condensed  by  a  cooling  arrangement 
and  the  hydrochloric  acid  evolved  is  led  into  water.  The 
product  is  washed  with  water  containing  a  little  caustic  soda, 
and  the  benzyl  chloride  freed  from  unaltered  toluene  and 
higher  substitution  products  by  distillation. 

It  is  a  colourless  liquid,  the  vapour  of  which  has  a  penetrating 
aromatic  smell,  rapidly  produces  a  flow  of  tears  and  attacks 
the  mucous  membrane  most  violently.  It  boils  at  176°  and 
has  a  sp.  gr.  of  1*107  at  14°.  As  it  undergoes  double  decom- 
position very  readily,  it  is  employed  for  the  preparation  of  the 
other  benzyl  compounds,  and  it  is  also  used  to  a  considerable 
extent  in  the  synthesis  of  the  higher  members  of  the  aromatic 
series.  It  is  also  technically  employed  in  the  manufacture  of 
benzaldehyde  and  in  the  colour  industry. 


1  Schiff  and  Pellizzari,  Ann.  Ghem.  Pharm.  ccxxi.  365. 

2  Beilstein  and  Geitner,  ibid,  cxxxix.  337. 


BENZYL  IODIDE.  97 


Benzyl  Iromide,  C6H5.CH2Br,  is  formed  by  the  action  of 
hydrobromic  acid  on  benzyl  alcohol,  and  by  that  of  bromine  on 
boiling  toluene.1  It  is  a  liquid  which  first  smells  like  cress  and 
then  like  mustard  oil ;  its  vapour,  like  that  of  the  chloride,  pro- 
duces a  flow  of  tears.  It  boils  at  198° — 199°,  and  has  a  sp.  gr. 
of  1-438  at  22°. 

Benzyl  iodide,  C6H5.CH2I,  was  obtained  by  Cannizzaro  in  the 
impure  state  by  the  action  of  iodine  and  phosphorus  on  benzyl 
alcohol.  Lieben  prepared  the  pure  compound  by  allowing  benzyl 
chloride  to  stand  in  the  dark  for  three  weeks  with  five  times  its 
weight  of  hydriodic  acid.2  It  is  also  formed  by  the  action  of 
potassium  iodide  on  benzyl  chloride,3  and  is  a  colourless,  crystal- 
line body,  the  vapour  of  which  produces  a  most  copious  flow 
of  tears;  it  is  only  slightly  soluble  in  alcohol,  but  readily  in 
ether  and  carbon  disulphide.  It  fuses  at  24°  to  a  liquid  which 
has  a  sp.  gr.  of  17335,  and  on  further  heating  becomes  coloured 
red,  decomposing  at  about  240°,  at  which  temperature  it  com- 
mences to  boil,  into  iodine,  hydriodic  acid,  and  a  hydrocarbon 
which  smells  like  toluene. 

Benzyl  nitrate,  C6H5.CH2.N03.  appears  to  be  formed  by  the 
action  of  silver  nitrate  on  benzylt  chloride :  the  product  of  the 
reaction  decomposes  on  distillation  with  an  energetic  evolution 
of  red  fumes,  the  distillate  consisting  of  benzaldehyde  and 
benzoic  acid.4 

The  same  products  are  obtained  by  treating  benzyl  iodide 
with  silver  nitrite.5 

2067  Benzyl  acetate,  C6H5.CH2  C2H3O2.    Cannizzaro  obtained 
this   compound   by   distilling   benzyl   alcohol   with   acetic  and 
sulphuric  acids,   as   well   as   by   heating   benzyl  chloride  with 
potassium  acetate,  and  alcohol.     It  is  a  liquid  which  possesses 
an  aromatic  odour,  boils  at  206°,  and  has  a  sp.  gr.  of  T057  at 
16'5°.6     It  is  converted  into  the  benzyl  ether  of  hydrocinnamic 
acid  or  benzylacetic  acid  by  the  action  of  sodium : 
4C6H5.CH2.O.CO.CH3  +  2Na  = 
2C6H5.CH2.O.CO.CH2.CH2.C6H5  +  2NaO.CO.CH3  +  H2. 

Boiling-point. 

Benzyl  propionate,  C7H7.O.C3H5O  219°— 220°. 

Benzyl  butyrate,       C7H7.OC4H7O  238°— 240°. 

1  Kekule,  Ann.   Chem.   Pharm.   cxxxvii.    139 ;   Cannizzaro,  ibid.    cxli.  198 ; 
Beilstein,  ibid,  cxliii.  369  ;  Lauth  and  Grimaux,  ibid.  cxlv.  113. 

2  Zeitschr.  Chem.  [2]  vi.  736.          3  V.  Meyer,  Ber.  Deutsch.  Chem.  Oes.  x.  311. 
Brunner,  Ber.  Deutsch.  Chem.  Ges.  ix.  1744.      5  van  Renesse,  ibid.  ix.  1454. 

6  Conrad  and  Hodgkinson,  Licbig's  Ann.  cxciii.  298. 
VOL.    III. — PART   IV. 


98  AROMATIC  COMPOUNDS. 

These  ethers  are  acted  upon  by  sodium  in  the  same  way  as  the 
acetate  (Conrad  and  Hodgkinson).  The  compounds  thus  formed 
will  be  subsequently  described. 

Benzyl  oxalate,  (C6H5.CH2)2C204,  is  formed  by  the  action  of 
benzyl  chloride  on  silver  oxalate,1  and  by  heating  benzyl  alcohol 
with  oxalic  acid.2  It  crystallizes  from  hot  alcohol  in  lustrous 
white,  scaly  crystals,  melting  at  80'5°. 

Isonitrosobenzyl  ether,  C6H5.CH2.O.Nz=CH.CO.CH3,  is  prepared 
by  heating  benzyl  chloride  with  a  solution  of  sodium  and 
isonitroso-acetone  (Part  I.  p.  572,  and  Part  III.  p.  170,  note)  in 
absolute  alcohol.  It  crystallizes  from  petroleum  ether  in 
colourless  tablets,  which  have  a  pleasant  smell  of  flowers  and 
melt  at  45°— 46°.3 

Acetoxime  benzyl  ether,  C6H5.CH2.ON=:C(CH3)2,  is  obtained 
in  a  similar  manner  from  acetoxime,  and  is  a  pleasant  smelling 
liquid  which  decomposes  into  acetone  and  benzylhydroxylamine 
when  boiled  with  concentrated  hydrochloric  acid  : 

C6H5.CH2.O.N=C(CH3)2  +  H2O^C6H5.CH2.O.NII?  |  CO(CH3)2. 

The  compound  actually  obtained  in  this  way  is  lenzylhydroxy- 
ammonium  chloride,  which  crystallizes  in  silvery  scales,  and 
is  converted  into  benzyl  iodide  by  heating  with  hydriodic 
acid  : 4 

C6H5.  CH2.O.NH3C1  +  3HI = C6H5.CH2I  +  NH4C1 + H20 + 12. 


SUBSTITUTION    PRODUCTS   OF   BENZYL 
ALCOHOL    AND    ITS   DERIVATIVES. 

2068  Substitution-products  are  not  formed  by  the  direct 
action  of  chlorine,  bromine,  or  nitric  acid  on  benzyl  alcohol, 
since  all  these  reagents  produce  oxidation.  Its  ethers,  how- 
ever, can  undergo  direct  substitution,  and  if  an  atom  of 
hydrogen  in  one  of  them  be  replaced,  para-compounds  are 
formed,  from  which  the  corresponding  alcohols  may  readily 

1  Beilstein  and  Kuhlberg,  Liebig's  Ann.  cxlvii.  341. 

2  Dumas  and  Dema^ay,  Compt.  Rend.  Ixxxiii.  688. 

3  Meyer  and  Ceresole,  Ber.  Deutsch.  Chcm.  Gcs.  xv.  3071. 

4  Janny,  ibid,  xvi  170. 


SUBSTITUTION  PRODUCTS  OF  BENZYL  ALCOHOL.        99 

be  obtained.  Thus,  parachlorobenzyl  alcohol,  C6H4C1.CH2.OH,  is 
prepared  by  boiling  its  chloride  or  bromide  with  water  : 

C6H4CLCH2Br + H2O  =  C6H4CLCH2OH  +  HBr. 

The  haloid  ethers  can  also  be  converted  into  the  acetate  by  boil- 
ing with  alcohol  and  potassium  acetate,  and  this  saponified  by 
heating  with  ammonia : 

C6H4C1.CH2.0.  C2H30  +  NH3  =  C6H4CLCH2.OH  +  C2H3O.NH2. 

The  higher  chlorinated  benzyl  chlorides  have  been  converted 
ito  their  alcohols  by  means  of  this  reaction. 
Paranitrobenzyl  alcohol  can  readily  be  prepared  by  nitrating 
jnzyl  acetate  or  oxalate  and  heating  the  product  with   am- 
lonia. 

Chlorine   substitution-products   of    benzyl   chloride    can    be 
)btained,  as  already  mentioned,  by  treating  it  with  chlorine  in 
cold  or  in  presence  of  iodine,  as  well  as  by  allowing  chlorine 
act  upon  the  vapour  of  boiling,  chlorinated  toluene.     Accord- 
to  Beilstein  and  Kuhlberg,  the  latter  is  the  better  method, 
id  is  now  generally  adopted. 

The  bromine  substitution-products  are  prepared  in  a  similar 
lanner;    the  use  of  this  method  has  shown  that  substitution 
loes  not  readily  take  place  in  the  methyl  group  when  bromine 
allowed  to  act  on  boiling  orthobromotoluene. 
Paranitrotoluene  is  converted  by  bromine  at  high  temperatures 
ito  paranitrobenzyl    bromide ;    paranitrobenzyl   chloride    and 
letanitrobenzyl  bromide  can  also  be  readily  obtained,  but  not 
le    ortho-compound.      If   orthonitrotoluene    be   heated    with 
>mine,  no  orthonitrobenzyl  bromide  is  found,  but  the  product, 
wording  to  Wachendorff,  consists  of  dibromorthonitrotoluene, 
"6H2Br2(N02)CH3,  which  is  not  attacked  by  potassium  acetate 
silver  acetate  even  at  1600.1     It  possesses  the  exceptional 
>roperty  of  dissolving  in  aqueous  alkalis  and  being  reprecipitated 
>y  mineral  acids,  and  Greiff  was  therefore  induced  to  examine  it 
more  carefully.  He  found  that  it  is  not  dibromonitrotoluene,  but 
the  isomeric  dibromortho-amidobenzoic  acid,C6H2Br2(NH2)C02H. 
Since  the  isomerides  of  orthonitrotoluene  behave  quite  differently 
towards  bromine,  it  follows  that  the  ortho-position  facilitates  a 
mutual  exchange  between  the  oxygen  of  the  nitroxyl  and  the 

1  Ann.  Chem.  Pharm.  clxxxv.  259. 


100  AROMATIC  COMPOUNDS. 

hydrogen  of  the  methyl.  How  this  intermolecular  change  takes 
place  has  not  yet  been  explained,  but  it  seems  probable  that 
orthonitrobenzyl  bromide  is  first  formed  and  is  then  con- 
verted by  the  nitroxyl  group  into  ortho-amidobenzoic  acid, 
just  as  benzyl  chloride  is  oxidized  to  benzoic  acid  by  nitric 
acid. 

2069  Parachlorobenzyl  alcohol,  C6H4C1.CH2.OH,  is  formed  by 
boiling  the  corresponding  bromide  or  chloride  with  water,1  or  by 
heating  parachlorobenzyl  acetate  to  100°  with  aqueous  ammonia.2 
It  is  readily  soluble  in  alcohol,  scarcely  in  cold,  but  somewhat 
more  readily  in  warm  water,  from  which  it  crystallizes  in  long 
needles  melting  at  70*5°  (Jackson  and  Field).  Oxidizing  agents 
convert  it  into  parachlorobenzoic  acid. 

Melting-point. 

Dichlorobenzyl  alcohol,3       C6H3C12.CH2OH,     needles         77° 
Trichlorobenzyl  alcohol,4     C^ClglCHgOH,     crystals 
Tetrachlorobenzyl  alcohol,5  C6HC14.CH2OH, 
Pentachlorobenzylalcohol,6C6Cl5.CH2.OH,    short  needles  193° 

Parachlorobenzyl  ethyl  ether,  C6H4C1.CH2.O.C2H5,  is  formed  by 
heating  parachlorobenzyl  chloride 7  or  parachlorobenzyl  acetate 8 
with  alcoholic  potash ;  it  is  a  liquid  which  boils  at  218°,9  and 
is  split  up  by  chlorine  in  the  cold  into  ethyl  chloride  and 
parachlorobenzaldehyde. 

Phenylchlorocarlylethyl  ether,  or  Benzylethoxyl  chloride,  C6H5. 
CHC1.0.C2H5,  is  prepared  by  boiling  benzylidene  chloride, 
C6H5.CHC12,  for  a  long  time  with  alcoholic  ammonia.  It  is  a 
liquid  which  boils  at  210° — 212°  and  is  converted  into  ethyl 
metanitrobenzoate,  C6H4(N02)CO.OC2H5,  by  nitric  acid.10 

Parachlorobenzyl  chloride,  C6H4C1.CH2C1,  is  obtained  together 
with  a  little  of  the  ortho-compound,  by  the  chlorination  of 
benzyl  chloride  in  presence  of  iodine,  and  by  the  action  of 
chlorine  on  boiling  monochlorotoluene,  as  a  liquid  which  boils 
at  213° — 2140.11  It  is  prepared  pure  from  parachlorotoluene  ; 12 
it  crystallizes  from  alcohol  in  lustrous  needles  or  prisms  which 

1  Jackson  and  Field,  Ber.  Deutsch.  Chem.  Ges.  xi.  905  ;  Amer.  Chem.  Journ. 
ii.  88. 

*  Beilstein  and  Kuhlberg,  Ann.  Chem.  Pharm.  cxlvii.  344. 

8  Ibid.  350.  *  Ibid.  clii.  241.  6  Ibid.  245.  6  Ibid.  246 
7  Naquet,  ibid.  Suppl.  [2]  250.                               8  Neuhof,  ibid,  cxlvii.  345 

9  Sintenis,  ibid.  clxi.  335. 

10  Hiibner  and  Bente,  Ber.  Deutsch.  Chem.  Ges.  vi.  805. 

11  Neuhof,  Ann.  Chem.  Pharm.  cxlvi.  320. 

12  Jackson  and  Field,  Ber.  Deutsch.  Chem.  Ges.  xi.  904. 


(PARABROMOBENZYL  ALCOHOL.  101 

3lt  at  29°,  readily  sublime,  and  possess  an  aromatic  vapour 
lich  attacks  the  mucous  membrane  very  violently. 
Melting-  Boiling- 

chloro-         ^  point.  point. 

benzyl-       V  C6H3C12.CH2C1,  liquid    .    .  241° 

hloride,1  j 
ichloro-  ^ 
benzyl-  VC6H2C13.CH2C1,  „  .  .  273° 

chloride,2     j 
Tetrachloro-  ) 

benzyl-       V  C6HC14.CH2C1,        „  296° 

chloride,3     j 
'entachloro-  \ 

benzyl-       I  C6C15.CH2C1,        fine  needles     103°      325°— 327° 
chloride,4     j 

Parachlorobenzyl     bromide,     C6H4Cl.CH2Br,    resembles     the 
iloride  very  closely ;  it  melts  at  48'5°.5 

Parachlorobenzyl   acetate,    C6H4C1.CH2  O.C2H3O,   is    obtained 
>y  boiling  the  chloride   with  potassium  acetate   and  absolute 
Icohol ;  it  is  a  liquid  which  boils  at  240°  and  has  an  aromatic 
lour.6 

Parabromobenzyl    alcohol,    C6H4Br.CH2.OH,  is   formed    when 
the  bromide  is  boiled  with  water  for  several  days ;  it  crystallizes 
from  a  hot  solution  in  flat,  elastic,  pearly  needles  which  have  an 
romatic  odour,  melt  at  69°,  and  only  volatilize  slowly  with  steam.7 
Parabromobenzyl  bromide,  C6H4Br.CH2Br.      This  compound  is 
prepared  by  passing  bromine  vapour  into  a  boiling  mixture  of 
parabromotoluene  and  orthobromotoluene,  which  is  obtained  by 
direct  bromination  of  toluene.     After  the  calculated  quantity 
been  added,  the  liquid  is  allowed  to  cool,  a  portion  of  the 
)romide  crystallizing  out  in  large,  rhombic  prisms.     The  mother- 
liquor  is  then  distilled  with  steam  in  which  the  ortho-  is  more 
lily  volatile  than  the  para-compound.      The  latter  can  also 
?adily  be  obtained  in  long,  thick,  transparent  prisms  by  allowing 
>romine  to  act  upon  the  mixture  of  bromotoluenes  in  the  sun- 
light.8    Parabromobenzyl  bromide  crystallizes  from  alcohol  in 
needles  which  melt  at  61°  and  are  volatile  with  steam ;  its  vapour 


1  Beilstein  and  Kuhlberg,  Ann.  Chem.  Pharm.  cxlvi.  146,  326. 

2  Ibid.  cl.  290.  3  Ibid.  299.  4  Ibid.  302. 
8  Field  and  Jackson,  loc.  cit. 

B  Neuhof,  Ann.   Chem.  Pharm.  cxlvii.  345. 

7  Jackson  and  Lowry,  Ber.  Dcutsch.  Chem.  Ges.  x.  1209. 

8  Schramm,  ibid.  xvii.  2922  ;  xviii.  350. 

238 


102  AKOMATIC  COMPOUNDS. 

has  a  pleasant,  aromatic  odour,  .but  attacks  the  eyes,  nose,  and 
throat  very  violently.1 

Pardbromobenzyl  acetate,  C6H4Br.CH2.O.C2H3O,  is  a  liquid 
which  has  a  pleasant  smell  resembling  that  of  acetic  ether,  and 
decomposes  on  distillation.2 

Metabromobenzyl  bromide,  C6H4Br.CH2Br,  is  obtained  in  a 
similar  manner  to  the  para-compound  ;  the  yield  is,  however,  very 
poor.  It  crystallizes  in  plates  or  needles  which  melt  at  41°,  and 
its  vapour  attacks  the  mucous  membrane  violently,  but  has 
a  somewhat  different  smell  from  that  of  the  para-compound. 
It  only  volatilizes  slowly  in  a  current  of  steam,  but  with  remark- 
able rapidity  in  ether  and  tolerably  readily  in  alcohol.  It  is  not 
attacked  by  chromic  acid  solution,  but  the  corresponding  alcohol, 
which  has  not  been  further  investigated,  is  oxidized  by  it  to 
metabromobenzoic  acid.3 

Orthdbromobenzyl  alcohol,  C6H4Br.CH2.OH,  crystallizes  from 
hot  water  in  flat  needles,  which  melt  at  80°,  and  readily  volatilize 
with  steam.4 

Ortholromolenzyl  bromide,  C6H4Br.CH2Br,  is  only  formed  with 
difficulty,  and  has  not  been  obtained  pure,  since  it  decomposes  on 
distillation.  It  is  an  oily  liquid,  which  does  not  solidify  at  —  15°, 
volatilizes  with  steam,  possesses  an  aromatic  odour,  and  rapidly 
attacks  the  mucous  membrane  ;  a  drop  placed  on  the  tongue 
causes  severe  pain.5  Sodium  acts  upon  its  ethereal  solution  with 
formation  of  various  products,  among  them  being  anthracene  : 

GH 


Para-iodolenzyl  alcohol,  C6H4I.CH2.OH,  crystallizes  from  carbon 
disulphide  in  scales  and  from  boiling  water  in  long  needles, 
which  have  an  aromatic  odour  and  melt  at  71  '7°.6 

Para-iodolenzyl  bromide,  C6H4I.CH2Br,  is  formed  by  the  action 
of  bromine  vapour  on  heated  para-iodotoluene,  and  crystallizes 
from  alcohol  in  flat,  white  needles,  which  melt  at  78'7°,  possess 
an  aromatic  odour,  and  attack  the  mucous  membrane  less 
violently  than  the  bromobenzyl  bromides.  Boiling  water  con- 
verts it  into  the  alcohol.7 

1  Schramm,  Ber.  Deutsch.  Chem.  Gcs.  viii.  1672  ;  ix.  931. 

2  Jackson  and  Lowry,  ibid.  x.  1209. 

3  Jackson  and  White,  Amcr.  Chem.  Journ.  ii.  315.     4  Jackson,  ibid.  viii.  932. 
8  Jackson,  Ber.  Dcutsch.  CJiem.  Ges.  ix.  932. 

6  Jackson  and  Mabery,  ibid.  xi.  56  ;  Amer.  Chem.  Journ.  ii.  251. 

7  Jackson  and  Mabery,  loc.  cit. 


PARANITROBENZYL  ALCOHOL. 


103 


2070  Paranitrobenzyl  a/c0M,-C6H4(NO2)CH2.OH,  is  prepared 
by  heating  its  acetate  or  oxalate  with  ammonia  to  1000,1  and  by 
the  action  of  caustic  soda  on  paranitrobenzaldehyde.2  It  crystal- 
lizes from  boiling  water  in  fine,  lustrous,  colourless  needles,  which 
become  coloured  in  the  air  and  melt  at  93°.  On  oxidation  it 
yields  paranitrobenzoic  acid. 

Paranitrobenzyl  chloride,  C6H4(NO2).CH2C1,  is  obtained,  to- 
gether with  the  ortho-  and  meta-compounds,  by  the  action  of 
concentrated  nitric  acid  on  benzyl  chloride,3  the  chloride  being 
gradually  added  to  the  acid  which  has  been  previously  cooled  to 
— 15°.4  It  is  also  formed  by  treating  paranitrotoluene  with 
chlorine  at  185° — 1900.5  It  crystallizes  from  boiling  alcohol  in 
fine,  white  needles,  or  small,  nacreous  plates,  which  melt 
at  76°. 

An  alkaline  solution  of  pyrogallol  reduces  it  to  paranitro- 
toluene.6 

Paranitrobenzyl  bromide,  C6H4(N02)CH2Br,  is  formed  when 
paranitrotoluene  is  heated  to  120° — 130°  with  bromine ;  the 
reaction  takes  place  at  70° — 80°  in  the  presence  of  ferrous 
bromide,  which  acts  as  a  bromine  carrier.7  On  the  gradual 
evaporation  of  its  solution  in  a  mixture  of  ether  and  alcohol,  it 
crystallizes  in  thin  tablets,  which  melt  at  99° — 100°.  It  destroys 
the  skin,  producing  a  burning  pain,  and  the  vapour  given  off  by 
its  hot  alcoholic  solution  attacks  the  mucous  membrane  most 
violently  (Wachendorff). 

Paranitrobenzyl  iodide,  C6H4(NO2)CH2I,  is  obtained  by  heat- 
ing the  chloride  with  potassium  iodide  and  alcohol;  it  crystallizes 
in  four-sided  tablets,  melting  at  127°,  and  its  vapour  produces 
a  flow  of  tears.8 

Paranitrobenzyl  nitrate,  C6H4(NO2)CH2NO3.  Beilstein  and 
Kuhlberg  prepared  this  compound  by  the  action  of  concentrated 
nitric  acid  on  the  alcohol,  and  believed  that  it  was  dinitrobenzyl 
alcohol.  Stadel  found,  however,  that  it  loses  nitric  acid  when 
heated  with  water  to  100°,  and  that  it  yields  paranitrobenzoic 
acid  on  oxidation,9  and  Orth  prepared  it  by  heating  the  chloride 

1  Beilstein  and  Kuhlberg,  Ann.  Chcm.  Pharm.  cxlvii.  343. 

Easier,  Bcr.  Dcutsch,  Chcm.  Gcs.  xvi.  2715. 

3  Beilstein  and  Geitner,  Ann.  Chcm.  Pharm.  exxxix.  327  ;  Grimaux,  ibid.  cxlv. 
146  ;  Abelli,  Gaz.  Chim.  Ital.  xiii.  97. 

*  Strakosch,  Bcr.  Dcutsch.  Chcm.  Gcs.  vi.  1056. 
B  Wacheudorff,  Ann.  Chcm.  Phann.  clxxxv.  271. 

6  Pellizzari,  Bcr.  Dcutsch.  Chcm.  Gcs.  xviii.   Ref.  150. 

7  Scheufeln,  Ann.    Chcm.  Pharm.  ccxxxi.  177. 

8  Kumpf,  ibid.  xvii.  1074.  '•>  Ibid.  xiv.  903. 


104  AROMATIC  COMPOUNDS. 

4 

with  alcohol  and  silver  nitrate.1  It  crystallizes  from  hot  water 
in  fine,  white  needles,  and  from  alcohol  in  long,  flat  needles, 
melting  at  71°. 

Paranitrolenzyl  acetate,  C6H4(NO.2)CH2.C2H3O2,  is  obtained 
by  dissolving  benzyl  acetate  in  well-cooled  concentrated  nitric 
acid  (Beilstein  and  Kuhlberg)  or  by  heating  the  chloride  with 
potassium  acetate  and  alcohol  (Grimaux).  It  crystallizes  from 
hot  alcohol  in  long,  pale  yellow  needles,  melting  at  78°. 

Paranitrobenzyl  oxalate,  (C6H4(N02)CH2)2C2O4,  was  obtained 
by  Beilstein  and  Kuhlberg  by  dissolving  benzyl  oxalate  in 
concentrated  nitric  aeid ;  on  heating  with  aqueous  ammonia 
it  is  converted  into  the  alcohol. 

2071  Metanitrobenzyl  alcohol,  C6H4(N02)CH2. OH,  was  prepared 
by  Grimaux,  together  with  metanitrobenzoic  acid,  by  the  action 
of  alcoholic  potash  on  metanitrobenzaldehyde  as  a  thick,  oily 
liquid,  which  decomposes  on  heating,  but  boils  at  178° — 180° 
under  a  pressure  of  3  mm.2 

Metanitrobenzyl  chloride,  C6H4(N02)CH2C1,  is  formed  by  the 
action  of  phosphorus  pentachloride  on  the  alcohol ;  it  crystallizes 
from  hot  petroleum  ether  in  long,  light  yellow  needles,  which 
melt  at  45° — 47°,  and  produces  painful  irritation  and  burning  on 
the  skin.3 

Orthonitrobenzyl  alcohol,  C6H4(N02)CH2.OH.  When  ortho- 
nitrotoluene  is  given  to  a  dog,  it  appears  in  the  urine  as  ortho- 
nitrobenzoic  acid,  and  as  the  urea  salt  of  uronitrotoluic  acidt 
2CpH15N09.CO(NH2)2  +  5H2O,  crystallizing  in  long  needles! 
which  are  very  readily  soluble  in  water,  slightly  in  cold  alcohol, 
and  insoluble  in  ether.  On  boiling  this  with  baryta  water  and 
decomposing  the  barium  salt  formed  with  sulphuric  acid,  uro- 
nitrotoluic acid,  C13H15N09,  is  obtained  as  a  crystalline  mass 
resembling  asbestos,  which  is  extremely  soluble  in  water  and 
alcohol  and  has  a  strongly  acid  reaction.  On  boiling  with  dilute 
sulphuric  acid  it  decomposes  into  a  syrupy  acid  and  orthonitro- 
benzyl  alcohol ; 4  this  compound  can  also  be  prepared  by  the 
action  of  caustic  soda  on  orthonitrobenzaldehyde.5  It  is  slightly 
soluble  in  water,  readily  in  alcohol  and  ether,  and  crystallizes  in 
long,  fine  needles,  which  melt  at  74°,  and  can  be  sublimed,  but 
detonate  when  rapidly  heated. 

1  Kumpf,  xv.  1136.  2  Zeitschr.  CJicm.  1867,  562. 

3  Gabriel  and  Borgraann,  Bf>r.  Deut*cli.  Chem.  Gcs.  xvi.  2064. 

4  Jaffe,  Hoppe-Seyler's  Zcfachr.  ii.  47. 

5  Friedlander  and  Henriques,  Btr.  Deutsch.  Chcm.  Ges.  xiv.  2801. 


SULPHUR  COMPOUNDS  OF  BENZYL.  105 

OrtTwnitrobenzyl  chloride,  C6H4(NO2)CH2C1,  is  formed,  as 
already  mentioned,  together  with  its  isomerides,  by  the  nitration 
of  benzyl  chloride,  and  was  first  isolated  from  the  product  by 
Kumpf.1  It  is  also  obtained  by  the  action  of  phosphorus  penta- 
chloride  on  the  alcohol.2  It  crystallizes  from  petroleum  ether  in 
large  rhombohedra  melting  at  48° — 49°. 

Orthonitrdbenzyl  iodide,  C6H4(N02)CH2I,  is  prepared  by  heat- 
ing the  chloride  with  potassium  iodide  and  alcohol;  it  forms 
rhombohedral  plates  melting  at  75°,  and  its  vapour  causes  a  flow 

tears. 

Orthamidoibenzyl  alcohol,  C6H4(NH2)CH2.OH,  is  obtained  by 
the  action  of  hydrochloric  acid  and  zinc-dust  on  orthonitrobenzyl 
Icohol  in  alcoholic  solution.  It  crystallizes  from  benzene  in 
rhite  needles,  which  melt  at  82°,  become  coloured  brown  in  the 

jht  or  in  the  air,  and  have  a  faint  smell  resembling  that  of 

liline. 

It  combines  with  acids  forming  soluble,  crystallizable  salts.3 


SULPHUR  COMPOUNDS  OF  BENZYL. 

2072  Benzyl  Jiydrosulphide,  or  Benzyl  mercaptan,  C6H5.CH2.SH. 
[arcker  obtained  this  compound  by  heating  benzyl  chloride  or 
mzyl  bromide  with  an  alcoholic  solution  of  potassium  hydro- 
ilphide.4     Otto  prepared  it  by  the  action  of  benzyl  chloride  on 
>tassium  thiosulphate,5  and  Bottinger  by  fusing  thiobenzalde- 
lyde,  C6H5.CSH,  with  caustic  potash,  benzyl  disulphide  and  a 
Little  benzoic  acid  being  simultaneously  formed.6 

It  is  a  colourless,  powerfully  refractive  liquid  which  has  an 
unpleasant  smell  of  leeks,  boils  at  195°,  and  has  a  sp.  gr.  of 
1'058  at  20° ;  its  vapour  produces  a  flow  of  tears.  It  gradually 
>xidizes  in  the  air,  more  rapidly  in  the  presence  of  ammonia  to 
benzyl  disulphide ;  an  ethereal  solution  of  bromine  produces  the 
same  effect. 

Mercury  benzyl  mercaptide,  (C6H5.CH2S)2Hg,  is  formed  by 
heating  the  hydrosulphide  with  mercuric  oxide ;  it  crystallizes 
from  alcohol  in  long,  silky  needles.  Mercuric  chloride,  in 

1  Friedlander  and  Henrique*,  xvii.  1073. 

J  Gabriel  and  Borgmann,  Ber.  Deutech.  Chem.  Ges.  xvi.  2064. 

Friedlander  and  Henriques,  ibid.  xv.  2109. 

|  Ann.  Chcm.  Phann.  cxxxvi.  75.  5  Zeitschr.  Chem.  [2]  vi.  23. 

6  Bcr.  Deutsch.  Chem.  Ges.  xii.  1055. 


106  AROMATIC  COMPOUNDS. 

alcoholic  solution,  gives  with  the  mercaptan  a  white  precipitate 
of  06H5.CH2.S.HgCl. 

Lead  benzyl  mercaptide,  (C6H5.CH2S)2Pb,  is  obtained  in  small 
yellow  plates  by  mixing  hot,  alcoholic  solutions  of  lead  acetate 
and  benzyl  mercaptan. 

Parachlorobenzyl  hydrosulphide,  C6II4C1.CH2.SH,  is  formed 
when  parachlorobenzyl  chloride  is  boiled  with  an  alcoholic  solu- 
tion of  potassium  hydrosulphide.  According  to  Beilstein,  it  is 
obtained  in  lustrous  crystals,  melting  at  84° — 850,1  while  accord- 
ing to  Jackson  and  White,  it  is  an  oily  liquid  which  possesses  a 
most  repulsive  and  penetrating  odour,  and  solidifies  on  cooling 
in  crystals  which  melt  at  19°—  20°.2 

Paranitrobenzyl  hydrosulphide,  C6H4(NO2)CH2.SH,  crystallizes 
from  alcohol  in  small,  colourless,  lustrous  plates,  melting  at  1400.3 

Benzyl  ethyl  sulphide,  C6H5.CH2.S.C2H5,  is  prepared  by  the 
action  of  ethyl  iodide  on  a  solution  of  sodium  in  benzyl  hydro- 
sulphide,  and  is  a  transparent  liquid,  which  boils  at  214° — 2160,4 
and  possesses  a  penetrating  odour  resembling  that  of  ordinary 
mercaptan. 

Orthobenzyl  thioformate,  (C6H5.CH2.S)3CH,  is  formed  when 
an  aqueous  solution  of  sodium  benzyl  mercaptide  is  heated 
with  chloroform ;  it  separates  from  hot  alcohol  in  colourless 
crystals,  melting  at  98°.  When  heated  with  fuming  nitric 
acid  to  250°,  it  is  decomposed  into  benzyl  mercaptan  and 
formic  acid.5 

Benzyl  sulphide,  (C6H5.CH2)2S.  Marcker  obtained  this  com- 
pound by  heating  benzyl  chloride  with  an  alcoholic  solution  of 
potassium  sulphide.  It  crystallizes  from  hot  alcohol  in  large, 
dazzling  white  plates,  and  from  ether  or  chloroform  in  large, 
thick,  rhombic  tablets,6  melting  at  49°. 

On  distillation  it  yields  stilbene,  C14H10,  and  sulphuretted 
hydrogen ;  dibenzyl,  C14H14,  tolallyl  sulphide,  C14H10S,  and  thio- 
nessal,  C28H20S,  are  simultaneously  formed. 

Methyl  iodide  and  benzyl  sulphide  react  even  in  the  cold, 
more  rapidly  on  warming,  with  formation  of  bcnzyldimethyl- 
sulphine  iodide,  C6H5.CH2(CH3)2SI,  and  trimethylsulphine  iodide, 


1  Beilstein,  Ann.  Chem.  Pharm.  cxvi.  347  ;  cxlvii.  346. 

2  Amer.  Chem,  Journ.  ii.  167. 

3  Strakosch,  Ber.  Dcutsch.  Chem.  Ges.  v.   598. 

4  Marcker,  Ann.  Chem.  Pharm.  cxl.  88. 

5  Dennstedt,  Ber.  Deutsch.  Chem.  Ges.  xi.  2265. 

6  Forst,  Ann.  Chem.  Pharm.  clxxviii.  671. 


SULPHUR  COMPOUNDS  OF  BENZYL.  107 

(CHg)3SI.     The  first  stage  of  the  reaction  is  represented  by  the 
following  equation  : 

2CH3I  +  (C6H6.CEg2S  =  (CH3)2S  +  2C6H6.CH2I. 

The  methyl  sulphide  then  combines  with  the  iodides  forming 
the  compounds  mentioned.  If  the  product  be  extracted  with 
water,  shaken  up  with  silver  chloride  and  the  filtrate  then 
fractionally  precipitated  with  platinum  chloride,  benzyl  dimethyl- 
sulphine  platinichloride,  (C6H5.CH2(CH3)2S)aPtCl6,  separates  out 
first  ;  it  crystallizes  from  water  in  long,  orange-red  needles.1 

Cahours,2  who  has  also  investigated  the  action  of  methyl 
iodide  on  benzyl  sulphide,  gives  the  following  equation  : 

3CH3I  +  (C6H5.CH2)2S  =  (CH3)3SI  +  2C6H5.CH2I. 

Benzyl  bromide  and  methyl  sulphide,  on  the  other  hand,  react 
the  following  way  : 

C6H5.CH2Br+2(CH3)2S  =  (CH3)3SBr+C6H5.CH2.S.CH3. 

If  methyl  alcohol  be  also  present,  benzyl  methyl  ether  is 
formed  instead  of  benzyl  methyl  sulphide  : 


C6H5.CH2Br  +  (CHg^S  +  2CH3.OH  - 
(CH3)3SBr  +  C6H5.CH2.O.CH3  +  H20. 

Benzyl  oxy  sulphide,  (C6H5.CH2)2SO,  is  formed  by  the  action  of 

oncentrated  nitric  acid  on  the  sulphide  ;  it  crystallizes  from 
cohol  in  small  plates  which  have  a  satin  lustre,  melt  at  1330,3 
d  are  converted  into  sulphuric  acid  and  benzoic  acid  by 
e  further  action  of  nitric  acid  (Marcker). 
Benzyl  disulphide,  (C6H5.CH2)2S2,  is  best  obtained  by  the 
tion  of  bromine  in  ethereal  solution  on  benzyl  mercaptan,  and 

s  also  formed   when   benzyl   chloride   is  treated   in   alcoholic 
lution  with  potassium  disulphide  ;  it  crystallizes  from  alcohol 
small,  lustrous  plates,  melting  at  66°  —  67°.     Nascent  hydrogen 
nverts  it  into  benzyl  mercaptan  (Marcker).     It  is  decomposed 

on  heating,  yielding  the  same  products  as  benzyl  sulphide. 
Benzyl  dioxy  sulphide,  or  Dibenzyl  sulphone,  (C6H5.CH2)2S02,  is 

formed  in  small  quantity  in  the  preparation  of  potassium  benzyl 

1  Scholler,  Ber.  Dcutsch.  Chem.  Ges.  vii.  1274. 

2  Compt.  Rend.  Ixxx.  1319. 

3  Otto  and  Liiders,  Ber.  Deutsch.  Chcm.  Ges.  xiii.  1284. 


108  AROMATIC  COMPOUNDS. 

sulphonate.1  It  may  readily  be  obtained,  however,  by  oxidizing 
benzyl  oxysulphide  with  potassium  permanganate  and  glacial 
acetic  acid  (Otto  and  Lliders) ;  it  is  insoluble  in  water,  and 
crystallizes  from  hot  alcohol  in  flat  needles,  which  melt  at  150°. 

2073  Benzylsulphonic  acid,  C6H5.CH2.S02.OH.  Bohler  pre- 
pared this  compound  by  boiling  benzyl  chloride  for  several 
hours  with  a  concentrated  solution  of  normal  potassium  sulphite, 
the  potassium  salt  obtained  being  converted  into  the  lead  salt, 
and  this  decomposed  with  sulphuretted  hydrogen.2  It  is  a 
deliquescent  crystalline  mass,  and  is  also  formed  by  the  oxidation 
of  benzyl  disulphide  with  nitric  acid.3  When  it  is  fused  with 
caustic  potash,  it  yields  benzoic  acid  (Vogt),  together  with  some 
benzene  and  a  larger  quantity  of  toluene.4 

Potassium  lenzylsulphonate,  C6H5.CH2.S03K  +  H2O,  crystal- 
lizes from  hot  water  in  well-developed  rhombic  prisms. 

Barium  lenzylsulphonate,  (C6H5.CH2.S03)2Ba  +  2H2O,  is 
obtained  by  the  addition  of  barium  chloride  to  the  solution  of 
the  potassium  salt;  it  forms  plates,  which  are  only  slightly 
soluble  in  water. 

Lead  lenzylsulphonate,  (C0H5.CH2.SO3)2Pb.  If  the  barium 
salt  be  decomposed  with  dilute  sulphuric  acid,  and  the  hot 
nitrate  saturated  with  lead  hydroxide,  the  basic  salt  C6H5.CH2. 
S03.PbOH,  is  obtained  as  a  lustrous,  crystalline  precipitate, 
which  is  converted  into  the  normal  salt  by  carbon  dioxide ;  this 
crystallizes  from  hot  water  in  lustrous  plates. 

Potassium  chlorolenzylsulphonate,  C6H4C1.CH2.SO3K  +  H20, 
is  prepared  from  chlorobenzyl  chloride  and  potassium  sulphite, 
and  crystallizes  in  needles;  barium  chloride  added  to  the 
potassium  salt  yields  barium  chlorolenzylsulphonate,  (C6H4C1. 
CH2.SO3)2Ba  +  H2O,  which  forms  colourless  lustrous  crystals. 

When  the  potassium  salt  is  fused  with  caustic  potash,  sali- 
cylic acid  and  parahydroxybenzoic  acid  are  formed  (Vogt  and 
Henniuger). 

Benzylsulphonic  chloride,  C6H5.CH2.S02C1.  Barbaglia  endea- 
voured to  prepare  this  compound  by  the  distillation  of  potassium 
benzylsulphonate  with  phosphorus  pentachloride,  but  only  ob- 
tained benzyl  chloride,  together  with  phosphorus  oxychloride 
and  some  thionyl  chloride.5  In  order  to  prepare  it,  the  potas- 
sium salt  is  treated  with  an  equal  weight  of  phosphorus  chloride 

1  Vogt  and  Henninger,  Ann.  Chem.  Pharm.  clxv.  375.  2  Ibid.  cliv.  50. 

8  Barbaglia,  Ber.  Deutsch.  Chem.  Ges.  v.  687. 

4  Otto,  ibid.  xiii.  1288.  5  Ibid.  v.  270. 


SELENIUM  COMPOUNDS  OF  BENZYL.  109 

and  the  mixture  gently  warmed  until  the  reaction  is  complete. 
The  product  is  then  washed  with  water  and  the  residue  crystal- 
lized from  ether.  Benzenesulphonic  chloride  forms  colourless 
prisms,  which  melt  at  92°  and  are  decomposed  when  more 
strongly  heated  into  benzyl  chloride  and  sulphur  dioxide ;  it  is  con- 
verted by  ammonia  into  benzylsulphonamide,  C6H5.CH2.SO2.NH2, 
rhich  crystallizes  from  water  in  prisms  melting  at  1050.1 

Nttrdbenzylsulphonic    acid,   C6H4(NO2)CH2.S03H,   is    formed 
)y  the  action  of  fuming  nitric  acid  on  barium  benzyl  sulphate, 
mixture  is  thus  obtained  which  contains,  together  with  the 
L-compound,  a  little  of  the  orthonitro-acid  and  the  dinitro- 
;id,  which  cannot  be  completely  separated.     On  boiling  with  a 
ixture    of  nitric    and    sulphuric    acids,  dinitrobenzylsulphonic 
nd,  C6H3(N02)2CH2.S03H,  is  obtained;  it  forms  salts,  which 
rystallize  well.     On   reduction   it  is   converted  into  diamido- 
lenzylsulphonic   acid,  C6H3(NH2)2CH2.SO3H,   which  crystallizes 
from  hot  water  in  silky  needles.2 


SELENIUM  COMPOUNDS  OF  BENZYL. 

2074  Benzyl  selenide,  (C6H5.CH2)2Se,  is  prepared  by  treating 
phosphorus  pentaselenide  with  alcoholic  soda  solution  in  absence 
of  air,  and  heating  the  sodium  selenide  thus  formed  with  benzyl 
hloride  to  the  boiling  point  of  the  latter.  When  the  solution 
Is,  benzyl  selenide  separates  out  first  and  then  some  benzyl 
elenide,  which  is  separated  by  recrystallization  from  hot 
hoi.  Benzyl  selenide  crystallizes  in  long,  white  needles 
transparent  prisms,  which  have  a  faint  aromatic  odour 
and  melt  at  45 '5°.  Like  methyl  selenide,  it  combines  with 
acids  forming  unstable  salts. 

Benzyl  diselenide,  (C6H5.CH2)2Se2,  is  obtained  by  boiling  crude 
sodium  selenide,  prepared  by  igniting  sodium  selenite  with  char- 
coal, with  alcohol  and  benzyl  chloride.  It  crystallizes  from  hot 
alcohol  in  straw-yellow,  fatty  scales,  which  melt  at  90°  and 
become  coloured  red  in  the  sunlight.  Nitric  acid  oxidizes  it 
to  benzylselenic  acid,  C^H^.CHg  Se02H,  crystallizing  from  hot 
water  in  needles  which  when  impure  possess  a  most  unpleasant 
smell,  which  is  not  nearly  so  strong  in  the  pure  compound.  It 
is  a  strong  acid. 

1  v.  Pechmann,  Ber.  Deutsck.  Chem.  Ges.  vi.  534. 

2  Mohr,  Ann.  Chcm.  Pharm.  ccxxi.  215. 


110  AEOMATIC  COMPOUNDS. 

When  benzyldiselenide  is  digested  for  some  days  with  methyl 
iodide,  a  black  mass  is  obtained  which  is  a  mixture  of  benzyl 
iodide,  trimethylselenine  iodide  and  lenzyldimethylselenine  tri- 
iodide : 

(C6H5.CH2)2  Se2+5CH3I  = 

C6H5.CH2I  +  (CBy.Se!  +  C6H5.CH2(CH3)2SeI3. 

The  latter  crystallizes  from  hot  alcohol  in  black,  heavy  needles 
which  have  a  metallic  lustre,  melt  at  65°  and  possess  a  repulsive 
odour.  They  commence  to  sublime  below  100°,  and  their 
vapour  attacks  the  eyes  violently.  If  the  alcoholic  solution  be 
treated  with  silver  nitrate,  the  excess  of  silver  removed  by 
hydrochloric  acid  and  the  filtrate  then  treated  with  platinum 
chloride,  a  precipitate  of  (C6H5.CH2.(CH3)2Se)2  PtCl6  is  obtained 
consisting  of  microscopic,  yellow,  quadratic  plates.1 


NITROGEN  BASES  OF  BENZYL. 

THE  BENZYLAMINES. 

2075  Cannizzaro  states  in  his  first  paper  on  the  alcohol  of 
benzoic  acid,  that  when  the  ethereal  chloride  prepared  from  it  by 
the  action  of  hydrochloric  acid  is  treated  with  alcoholic  ammonia, 
a  base  which  differs  from  toluidine  is  formed  (p.  89).  Three 
years  later  he  found  that  this  is  tribenzylamine,  (C7H7)3N.2  In 
the  year  1862,  Mendius  made  the  important  discovery  that  the 
nitrils  of  the  fatty  acids  combine  with  hydrogen  to  form  amines, 
and  that  those  of  the  aromatic  series  behave  in  a  similar  manner, 
inasmuch  as  benzonitril,  C7H5N,  yields  a  powerful  base,  C7H9N, 
which,  however,  is  not  identical  with  toluidine,  "  as  might  have 
been  expected  from  the  hitherto  accepted  views  as  to  the  re- 
lations of  the  bases  homologous  with  aniline  to  the  corresponding 
members  of  the  benzoic  acid  series,"  but  differs  both  from  it  and 
the  isomeric  methylaniline  in  its  properties.  It  also  appeared 
to  him  improbable  that  it  was  identical  with  the  lutidine  con- 
tained in  coal-tar  oil ;  he,  therefore,  decided,  in  the  absence  of  a 
careful  comparison  between  the  two  substances,  "to  introduce 

1  Loring  Jackson,  Ann.  Chcm.  Phann.  clxxix.  8. 

2  Jahresb.  1856,  582. 


NITROGEN  BASES  OF  BENZYL.  ill 


the  base  prepared  from  benzonitril  into  scientific  literature  as  a 
new  compound  and  to  denote  it  by  a  new  name." x  Two  years 
later,  Cannizzaro  published  a  paper  on  "  The  Amines  of  Benzyl 
Alcohol "  in  which  he  says  "  Toluidine,  C7H9N,  is  generally  looked 
upon  as  the  primary  benzylamine.  I  have  obtained  results  which 
do  not  agree  with  this  supposition."  He  found  that  the  primary 
benzylamine,  which  he  had  prepared  from  benzyl  cyanate  (benzyl 
isocyanurate),  is  a  strong  base  resembling  ethylamine  and  amyla- 
mine  in  its  properties.  He  also  obtained  it,  together  with  dibenzyl- 
amine  and  triberizylamine,  by  heating  benzyl  chloride  with 
alcoholic  ammonia,2  and  described  the  separation  of  these  bases 
and  the  properties  of  benzylamine.3  In  order  to  prepare  the 
latter,  a  mixture  of  benzyl  chloride  and  alcoholic  ammonia  is 
allowed  to  stand  for  some  days ;  a  portion  of  the  tribenzylamine 
separates  out  in  crystals,  and  a  further  quantity  is  left  behind 
when  the  alcohol  is  removed  from  the  filtrate  by  distillation 
and  the  residue  treated  with  hot  water.  The  solution  is 
then  evaporated  to  dryness,  and  the  most  soluble  portion  of 
the  residue,  consisting  chiefly  of  benzylamine  hydrochloride  is 
separated  by  fractional  crystallization.  This  is  then  decomposed 
by  caustic  potash  and  the  base  allowed  to  remain  in  contact 
with  some  solid  potash  in  order  to  dry  it,  and  at  the  same  time 
avoid  exposure  to  carbon  dioxide.  It  is  then  purified  as  much 
as  possible  by  fractional  distillation  and  treated  with  dry  carbon 
dioxide ;  a  solid  compound  is  formed  which  is  washed  with 
anhydrous  ether  to  remove  the  last  adhering  traces  of 
dibenzylamine.  The  residue  is  then  converted  into  the  crystal- 
lized hydrochloride  and  the  pure  base  finally  liberated  by  caustic 
potash. 

According  to  Limpricht,  the  base  is  prepared  by  heating 
benzyl  chloride  with  a  solution  of  ammonia  in  commercial 
absolute  alcohol  for  twenty-four  hours  in  a  steam  bath  and  re- 
moving free  ammonia  and  the  largest  portion  of  the  alcohol  by 
distillation.  The  residue  is  treated  with  water  to  precipitate 
the  mixed  bases,  which  are  then  dissolved  in  alcohol  and  treated 
with  hydrochloric  acid,  the  acid  solution  being  allowed  to  cool 
gradually.  Tribenzylamine  hydrochloride  separates  out  in  prisms 
or  needles,  and  a  mixture  of  this  salt  with  plates  of  dibenzyl- 
amine hydrochloride  is  obtained  by  the  concentration  of  the 
mother-liquor ;  the  residual  liquid  after  repeated  evaporation 

1  Ann.  Chcm.  Pharm.  cxxi.  144.     2  Ibid,  cxxxiv.  128.     3  Ibid.  Suppl.  iv.  24. 


112  AROMATIC  COMPOUNDS. 

to  a  syrup,  solution  in  hot  water  and  reconcentration,  yields 
benzylamine  hydrochloride.  The  water  employed  for  the 
precipitation  of  the  hases  contains  some  benzylamine,  which 
may  be  extracted  by  saturating  the  liquid  with  hydrochloric 
acid,  evaporating  to  dryness  and  extracting  with  hot  absolute 
alcohol,  which  leaves  ammonium  chloride  undissolved.  The 
hydrochlorides  of  di-  and  tri-benzylamine  are  purified  by 
re-crystallization  from  water  or  alcohol. 

The  primary  base  is  always  present  in  the  smallest  quantity, 
while  the  relative  amounts  of  the  other  two  are  very  variable ; 
sometimes  a  large  quantity  of  tribenzylamine  is  formed  with 
only  traces  of  dibenzylamine,  while  in  other  cases  the  relation 
is  the  inverse  of  this. x 

2076  Benzylamine,  C6H5.CH9.NH2.  Mendius  obtained  this 
compound  by  treating  benzonitril  in  alcoholic  solution  with  zinc 
and  hydrochloric  acid,  freeing  the  solution  from  alcohol  and 
unattacked  nitril  by  distillation,  saturating  the  residue  with 
caustic  potash  and  extracting  the  benzylamine  with  ether.  The 
ethereal  solution  is  then  treated  with  hydrochloric  acid,  the 
benzylamine  hydrochlorid.e,  which  is  obtained  on  evaporating 
the  solution,  re-crystallized  from  absolute  alcohol  and  the  pure 
base  then  set  free  by  caustic  potash. 

Hofmann  obtained  benzylamine  by  the  action  of  zinc  and 
hydrochloric  acid  on  thiobenzamide,  C6H5.CS.NH2,2  which  is 
formed  by  the  direct  combination  of  sulphuretted  hydrogen  with 
benzonitril : 

C6H5.CS.  NH2  +  4H  =  C6H5.CH2.NH2 + H2S. 

Both  these  methods  are  tedious,  and,  like  the  preparation  from 
benzyl  chloride  and  ammonia,  only  give  a  small  yield.  Benzyl- 
amine can,  however,  be  readily  prepared  in  large  quantities  by 
heating  benzyl  chloride  with  an  equivalent  amount  of  silver 
cyanate,  until  the  violent  reaction  has  ceased;  a  mixture  of 
benzyl  isocyanate  and  benzyl  isocyanurate  is  formed  and  after 
distillation  is  re-distilled  over  caustic  potash.  The  product  thus 
obtained  contains  some  di-  and  tri-benzylamine,  since  the  mix- 
ture of  isocyanates  always  contains  some  benzyl  chloride.  These 
can  be  removed  by  converting  the  whole  into  the  hydrochlorides 
or  by  extracting  the  benzylamine  by  shaking  out  witlrwater. 

1  Ann.  Chem.  Pharm.    cxliv.  304. 

2  Ber.  DeiOsch.  Chem.  Ges.  i.  102. 


BENZYLAMINE.  113 

. — . . 

It  is  then  converted  into  the  hydrochloride  which  is  decomposed 
by  caustic  potash,  and  the  base  dried  over  solid  potash  and 
redistilled. l 

It  can  also  be  readily  obtained  by  decomposing  benzylacet- 
amide,  C6H5.CH2.NH.(C2H30),  which  is  prepared  by  the  action 
of  benzyl  chloride  on  acetamide,  with  alcoholic  potash.2 

Another  simple  method  of  preparation  has  been  found  by 
Hofmann.  On  heating  benzyl  chloride  with  potassium  cyanide, 
phenylacetonitril,  C6H5.CH2.CN,  is  obtained ;  when  water  is 
added  to  a  solution  of  this  compound  in  concentrated  sulphuric 
acid,  phenylacetamide,  C6H5.CH2.CO.NH2  is  precipitated.  This 
is  then  treated  with  a  molecule  of  bromine,  a  5  per  cent,  solution 
of  four  molecules  of  caustic  potash  added  with  continual  agita- 
tion and  the  liquid  heated  by  a  current  of  steam  :  a  mixture  of 
benzylamine  and  brominated  benzylamine  distils  over,  which  is 
converted  into  pure  benzylamine  when  allowed  to  stand  for 
some  time  over  sodium  amalgam,  all  the  bromine  being  replaced 
by  hydrogen.3 

Hofmann  has  shown  that  the  amides  of  other  monobasic  acids 
can  readily  be  converted  by  this  reaction  into  amines  containing 
one  atom  of  carbon  less  in  the  molecule.  He  has  carefully 
investigated  the  course  of  the  reaction  in  the  case  of  acetamide, 
and  finds  that  acetbromamide,  CH3.CO.NHBr,  is  first  formed, 
and  that  this  loses  hydrobromic  acid  with  formation  of  methyl 
isocyanate,  which  assumes  the  elements  of  water  and  splits 
up  into  carbon  dioxide  and  methylamine. 

Benzaldehyde,  which  is  now  a  cheap  commercial  product,  can 
also  be  readily  converted  into  benzylamine.  It  combines  with 
hydrocyanic  acid  to  form  phenylhydroxyacetonitril,  C6H5.CH 
(OH2)CN,  which  is  converted  by  treatment  with  alcoholic 
ammonia  into  phenylamido-acetonitril,  C6H5.CH(NH2)CN. 
On  boiling  this  with  dilute  sulphuric  acid,  phenylamido- 
acetic  acid  is  formed  and  decomposes  into  benzylamine  and 
carbon  dioxide  on  distillation.  These  products  of  decom- 
position recombine  to  some  extent  forming  benzylammonium 
benzylcarbamate  (p.  114),  which  is,  however,  readily  decomposed 
by  alkalis.  Pure  benzylamine  hydrochloride  may  also  be 
obtained  by  treating  the  distillate  with  hydrochloric  acid.4 

Properties. — Benzylamine   is  a  colourless  liquid  which  has  a 

1  Strakosch,  Bcr.  Deutsch.  Chem.   Ges.  v.  692. 

2  Rudolph,  ibid.  xii.  1297.  3  Ibid,  xviii.  2734. 
4  Friedlander  and  Tiemann,  ibid.  xiv.  1969. 


114  AROMATIC  COMPOUNDS. 

characteristic,  faint,  aromatic  odour,  does  not  become  coloured 
in  the  light,  boils  at  185°  and  has  a  sp.  gr.  of  O990  at  14°. 
It  is  soluble  in  water  in  every  proportion,  but  is  insoluble 
in  strong  alkalis,  and  is  therefore  precipitated  by  caustic 
potach  from  its  aqueous  solution.  It  has  a  strong  alkaline 
reaction,  fumes  with  hydrochloric  acid  and  rapidly  absorbs 
carbon  dioxide,  so  that  a  drop  exposed  to  the  air  is  soon 
converted  into  small,  silky  needles  of  the  carbonate.  It 
combines  with  benzyl  chloride  to  form  dibenzylamine  hydro- 
chloride. 

Benzylamine  hydrochloride,  C7H7NH3C1,  forms  quadratic 
tablets,  very  soluble  in  water  and  alcohol ;  its  platinichloride 
is  a  granular,  crystalline  precipitate. 

Benzylamine  nitrite,  C7H7NH3.N02,  is  obtained  by  shaking 
the  hydrochloride  with  silver  nitrite  and  ether.  It  is  extracted 
from  the  silver  chloride,  which  is  simultaneously  formed,  by 
cold  absolute  alcohol,  and  is  deposited  on  the  evaporation  of 
this  solution  in  well-formed  crystals,  which  decompose  with 
evolution  of  nitrogen  when  gently  warmed.1 

Benzylammonium  benzylcarbamate  is  formed  by  the  com- 
bination of  benzylamine  with  carbon  dioxide  : 

/ONH3(CH2.C6H6) 
C02+ 2NH.2.CH2.C6H5  =  CO< 

\NH(CH2.C6H5). 

It  is  readily  soluble  in  water,  volatilizes  when  the  solution  is 
boiled,  and  crystallizes  from  alcohol  in  small,  lustrous  plates 
which  melt  at  .99°. 

2077  Dibenzylamine,  (C6H5.CH2)2NH,  is  a  thick  liquid, 
which  has  a  sp.  gr.  of  T033  at  14°  and  is  insoluble  in  water,  but 
readily  soluble  in  alcohol.  When  a  small  quantity  is  rapidly 
heated  it  distils  unaltered  at  above  300°,  but  on  gradual  distilla- 
tion it  is  decomposed  with  formation  of  ammonia,  toluene, 
dibenzyl,  C14H14,  stilbene,  C14H12,  lophine,  C21H16N2,  and  other 
bodies.2  When  heated  to  260°  in  a  stream  of  hydrochloric  acid, 
it  gradually  and  incompletely  decomposes  into  benzyl  chloride 
and  benzylamine  hydrochloride,  while  at  100°  it  combines  with 
benzyl  chloride  forming  tribenzylamine.  On  treatment  with 

1  Curtius,  Bcr.  Dcutsch.  Chem.  Got.  xvii.  958. 

2  Bruuner,  Ann.  C'fiem.  Pfiarm.  cli.  131. 


DIBENZYLAMINE. 

bromine  and    a   large    quantity  of  water,  it   decomposes   into 
benzylamine  and  benzaldehyde : 

(C6H5.CH2)2NH  +  H.,0+Br2= 
C6H5.COH+C6H5.CH2.NH2+2HBr. 

Iodine  has  a  similar  action  but  requires  a  temperature  of 
140°  (Limpricht). 

Dibenzylamine  hydrochloride,  (C7H7)2NH2C1,  is  readily 
soluble  in  hot  water  and  alcohol,  but  much  less  freely  in  the 
cold,  and  crystallizes  in  large,  flat,  prisms,  or,  when  its  alcoholic 
solution  is  rapidly  cooled,  in  thin  plates.  The  hydrobromide 
and  hydriodide  are  very  similar. 

Dibenzylamine  nitrate,  (C7H7)2NH2.N03,  is  less  soluble  than 
the  other  salts  and  crystallizes  in  flat  needles  or  prisms. 

Tribenzylamine,  (C6H5.CH2)3N,  is  also  formed,  together  with 
other  bodies,  when  benzaldehyde  is  gradually  heated  to  180° 
with  ammonium  formate.  Formamide  is  the  first  product  and 
decomposes  into  carbonic  oxide  and  ammonia,  which  then  act 
upon  the  benzaldehyde : 

3C6H5.COH  +  SCO  +  NH3  =  (C6H5.CH2)3N  +  3CO2. 

This  is  the  most  convenient  method  for  the  preparation  of 
tribenzylamine,  100  grms.  of  benzaldehyde  yielding  40  grms. 
of  the  pure  product.1  It  is  slightly  soluble  in  cold  alcohol 
and  crystallizes  from  a  hot  solution  in  needles,  plates,  or 
monoclinic  tablets  (Panebianco)  melting  at  91°.  Small 
quantities  can  be  distilled  without  decomposition,  but  larger 
quantities  split  up,  yielding  the  same  products  as  the  secondary 
base.  It  also  resembles  the  latter  in  its  behaviour  towards 
bromine  and  iodine,  benzaldehyde  and  dibenzylamine  being 
formed.  When  its  hydrochloride  is  heated  to  250°  in  a  stream 
of  hydrochloric  acid,  it  decomposes  into  benzyl  chloride  and 
dibenzylamine  hydrochloride,  while  Lauth  obtained  benzyl 
chloride  and  ammonium  chloride  by  treating  the  free  base  in  a 
similar  manner  at  180° 2.  It  does  not  combine  with  benzyl 
chloride,  and  hence  no  tetrabenzylammonium  chloride  is  formed 
in  its  preparation  from  benzyl  chloride  and  ammonia ;  it  com- 
bines with  ethyl  iodide,  however,  on  heating  to  form  a  crystal- 
lized compound,  which  does  not  yield  a  hydroxide  on  treatment 
with  silver  oxide,  but  decomposes  into  its  constituents. 3  It 

1  Leuckart,  Ber.  Deutsch.  Chcm.  Ges.  xviii.  2341. 

2  Ibid.  vi.  678.  3  Vasca-Lanza,  ibid.  vii.  82. 


1 16  AROMATIC  COMPOUNDS. 

also  forms  a  crystallized  compound  when  heated  with  methyl 
sulphate  to  1000.1 

The  salts  of  tribenzylamine  have  been  crystallographically 
investigated  by  Panebianco.2 

Tribenzylamine  hydrochloride,  (C7H7)3NHC1,  is  slightly  soluble 
in  cold  alcohol  and  water,  and  crystallizes  from  its  hot  solution 
in  quadratic  prisms.  It  decomposes  above  270°,  a  large  quantity 
of  toluene  being  formed  (Rohde).  The  platinichloride  crystal- 
lizes in  orange-coloured,  monoclinic  needles. 

Tribenzylamine  nitrate,  (C7H7)3NHNO3,  forms  rhombic 
crystals  which  are  insoluble  in  water  and  slightly  soluble  in 
alcohol. 

Tribenzylamine  sulphate,  (C7H7)3NH).2SO4,  forms  monoclinic 
crystals,  is  insoluble  in  water,  slightly  soluble  in  alcohol,  and 
combines  with  aluminium  sulphate  forming  tribenzylammonium 
alum,  (C21H22N)2A12(SO4)4  +  24H20,  which  is  deposited  in  regular 
crystals  and  is  soluble  in  water  but  not  in  alcohol. 

Nitrosodibenzylamine,  (C7H7)2N(NO).  Rohde  obtained  this 
compound,  together  with  benzaldehyde,  by  distilling  a  con- 
centrated alcoholic  solution,  of  tribenzylamine  with  nitric 
acid : 


CH2.C6H5  /CH2.C6H5 


-CH2.C6tT5  +  NO2.OH  =  N-NO  +  COH.C6H5+H9O. 

\GBLOH.  \CH*CLH. 


It  is  readily  soluble  in   alcohol  and  ether,  and  crystallizes  in 

quadratic  tablets,  melting   at  52°;    it  does   not  combine  with 

acids,  and  is  converted  into   dibenzylamine  by  the   action   of 
nascent  hydrogen  or  hydrochloric  acid. 


AMIDO-SUBSTITUTED  BENZYLAMINES. 

2078  I>iethylbenzylamine,  C6H5.CH2.N(C2H5)2,  is  obtained  by 
heating  benzylamine  with  ethyl  iodide,  or  benzyl  chloride  with 
diethylamirie.  It  is  a  transparent,  oily  liquid,  which  boils  at 
211° — 212°,  and  combines  with  ethyl  iodide  on  heating  with 
formation  of  triethylbenzylammonium  iodide,  N(C6H5.CH2) 
(C2H5)3I,  which  can  also  be  prepared  from  benzyl  iodide  and 

1  Claessou  and  Lundvall,  Eer.  Dcutseh.  Chem.  Gcs.  xiii.  1703. 

2  Jahresb.  1878,  476. 


ETHYLBENZYLAMINE.  117 

triethylamine,  and  forms  large,  colourless  crystals,  which  are 
readily  soluble  in  water ;  on  dry  distillation  it  is  decomposed 
into  triethylamine  and  benzyl  iodide,  while  it  is  not  attacked 
when  heated  with  concentrated  hydriodic  acid.1  When  iodine 
is  added  to  it  in  alcoholic  solution,  the  periodide,  N(C6H5.CH2) 
(C2H5)3I3,  separates  out  in  black-blue  monoclinic  prisms,  which 
have  a  metallic  lustre. 

Ethyldibenzylamine,  (C6H5.CH2)2NC2H5,  was  obtained  by 
Limpricht  from  ethyl  iodide  and  dibenzylamifie ;  it  is  an  oily 
liquid. 

Dietliyldibenzylammonium  iodide,  (C6H5.CH2)2(C2H5)2NI,  is 
formed  by  the  combination  of  diethylbenzylamine  with  benzyl 
iodide.  It  crystallizes  from  hot  water  in  needles  possessing  a 
diamond  lustre  ;  when  it  is  distilled  with  hydriodic  acid,  benzyl 
iodide  is  liberated  (V.  Meyer). 

Benzylphenylamine,  or  Benzylaniline,  C6H5.CH2.N(C6H5)H,  is 
formed  when  benzyl  chloride  is  heated  with  aniline  to  160°. 
The  free  base  crystallizes  from  hot  alcohol  in  four-sided  prisms, 
melting  at  32°.2  It  may  also  be  obtained  by  the  action  of 
hydrochloric  acid  and  zinc-dust  on  thiobenzanilide,3  C6H5.CS.N 
(C6H5)H. 

Benzylphenyldimethylammonium  chloride,  (C6H5.CH2)  C6H5 
(CH3)2NC1,  is  readily  formed  by  the  direct  combination  of 
benzyl  chloride  with  dimethylaniline.  It  crystallizes  from  water 
or  alcohol  in  tablets,  which  melt  at  110°,  and  is  split  up  into  its 
constituents  by  distillation.  It  is  not  decomposed  by  boiling 
with  water  and  silver  oxide,  but  its  decomposition  may  be 
effected  by  employing  silver  sulphate.  If  the  sulphuric  acid  be 
removed  by  baryta  water  from  the  solution  thus  formed,  and  the 
filtrate  concentrated,  the  hydroxide  is  obtained  as  a  strongly 
alkaline,  syrupy  mass,  which  is  converted  into  the  carbonate  in 
the  air.  On  distillation  it  decomposes  smoothly  into  dimethyl- 
aniline  and  benzyl  alcohol,4  while  tetra-ethylammonium  hydroxide 
under  similar  conditions  yields  triethylamine.  ethylene  and 
water. 

Eenzyldiphenylamine,  C6H5.CH2.N(C6H5)2,  is  formed  when 
diphenylbenzothiamide,  C6H5.CS.N(C6H5)2,  is  treated  with 
hydrochloric  acid  and  zinc-dust.  It  crystallizes  from  hot  alcohol 

-a\  *f  denburS  and  Struve,  Her.  Deutsch.   Cham.  Gcs.  x.  43  ;  Ladenburg,  ibid.  x. 
561,  1153,  1634  ;  V.  Meyer,  ibid.  x.  309,  964,  1291. 
Fleischer,  Ann.  Chcm.  Pharm.  cxxxviii.  22. 
Bern thsen  and  Trompetter,  Bcr.  Deutsch.  Chcm.  GM.  xi.  1760. 
*  Michler  arid  Gradmaun,  ibid.  x.  2079. 

239 


118 


AROMATIC  COMPOUNDS. 


in  long  white  needles  which  melt  at  87°,  and  does  not  combine 
with  acids  (Bernthsen  and  Trompetter). 

Dibenzyltolylamine,  (C6H5.CH2)2NC6H4.CH3.  This  base,  which 
is  also  known  as  dibenzyltoluidine,  was  prepared  by  Cannizzaro 
by  heating  paratoluidine  with  alcohol  and  benzyl  chloride.  It 
crystallizes  from  hot  alcohol  in  very  fine  needles,  melting  at 
54*5°  —  55°,  and  is  a  weak  base  ;  it  differs  from  the  isomeric 
tribenzylamine  in  forming  salts  which  are  decomposed  by  water.1 


SUBSTITUTION   PRODUCTS    OF  THE 
BENZYLAMINES. 

2079  These  are  formed  by  the  action  of  ammonia  on  the 
corresponding  haloid  ethers. 

Halogen  substitution  products.  These  compounds  are  strong 
bases  and  form  crystalline  salts ;  the  primary  compounds  absorb 
carbon  dioxide  from  the  air. 

Melting-point. 


Paratrichloro- 
benzylamine,* 

Paratribromo- 
benzylamine 


-    ) 
M 


CAC1.CH,NH2,   liquid     . 
crstals  . 


(  rhombic  ) 
j  prisms  j- 


prisms 


J^AICH^NH,    needles  .    . 


20° 

78-5° 
78°— 79C 

76° 
114-5° 


Paratri-iodo-      |  (C  H4I.CH2)3N,       needles  . 
benzylamiue,8  J  v   6    4 

Orthobromo-      I  c  H  Br  CH  NH     u     id     . 

benzylamme,9  j 


1  Ann.  Chem.  Pharm.  Suppl.  iv.  80. 

2  Bei-lin,  Ann.  Chem.  Pharm.   Suppl.  cli.   137  ;   Jackson  and  Field,  Amer. 
Chem.  J<nirn.  ii.  95.  3  Ibid.  4  Ibid. 


5  Jackson  and  Lowry,  Per.  Dcutsch.  Chem.  Ges.  x.  1211. 

6  Jackson  and  Mabery,  Amer.  CJiem.  Journ.  ii.  257. 

7  Ber.  Dcutsch.  Chem.  Ges.  xi.  58. 

9  Jackson  and  White,  Amer.  Chem.  Journ.  ii.  317. 


8  Ibid. 


NITROBENZYLAMINES.  119 

Melting-point. 

Orthodibromo-  1  /p  TT  T>r.  nw  *\  ATTT  /  rhombic  |  „„<> 

i       •      T    r  (L/A-tlxj3r.Uxl0)nJN  ±1  •<          x  i     r  oo 

benzylamme,1  j  ^   €  (  crystals  j 

Orthotribromo-  |  /p  TT  Br  CH  ^  N      crvstals  1 21'5°     1 22° 

1  '          9        L    \  V^cAl^-Dl.  •  v^-LJ-oyoi-N ,        ClyotcHQ    .       .  JL^i.  c>  J.*£<£ 

benzylamme,2    j  v   e 

Paranitrobenzylamines  have  been  prepared  by  Strakosch  by 
heating  paranitrobenzyl  chloride  with  aqueous  ammonia  to 
100°.  The  primary  base  could  not  be  isolated ;  the  secondary 
base  combines  with  acids,  while  the  tertiary  does  not,  thus 
rendering  the  separation  of  these  two  a  matter  of  no  difficulty.3 

Paradinitrobenzylamine,  (C6H4(NO2)CH2)2NH,  crystallizes 
from  hot  alcohol  in  large,  yellowish,  lustrous  plates,  melting 
at  93°;  its  hydrochloride  forms  lustrous,  yellow  prisms,  which 
are  only  slightly  soluble  in  water  and  alcohol,  while  its  platini- 
chloride,  which  crystallizes  in  yellow  needles,  is  almost  insoluble. 

Paratrinitrobenzylamine,  (C6H4(NO2)CH2)3N,  is  slightly 
soluble  in  hot  alcohol,  readily  in  glacial  acetic  acid  and  nitro- 
benzene, and  crystallizes  in  lustrous,  white  needles,  which  melt 
at  163°,  and  possess  a  pleasant  odour. 

Paranitrobenzylphenylamine,  C6H4(N  02)CH2.N(C6H5)H,  is 
formed  by  heating  paranitrobenzyl  chloride  with  aniline ;  it 
crystallizes  from  hot  alcohol  in  pointed,  lustrous,  yellow  needles. 
Its  hydrochloride  crystallizes  from  hot  hydrochloric  acid  in  small 
lustrous  plates  which  are  decomposed  by  water  with  separation 
of  the  base  (Strakosch). 

Metanitrobenzylamines.  Aqueous  ammonia  converts  meta- 
nitrobenzyl  chloride  into  the  secondary  and  tertiary  amines, 
while  in  the  presence  of  alcohol  only  the  former,  together  with 
a  small  quantity  of  the  primary  base,  is  formed.4 

Metanitrolenzylamine,  C6H4(N02)CH2.NH2,  is  a  yellow,  oily 
liquid,  which  becomes  solid  in  the  air  from  absorption  of  carbon 
dioxide.  Its  oxalate  crystallizes  in  needles,  which  are  only 
slightly  soluble  in  water. 

Metadinitrobenzylamine  crystallizes  from  alcohol  in  small 
yellow,  rhombic  plates,  melting  at  87°.  Its  hydrochloride  and 
platinichloride  are  only  slightly  soluble  in  water. 

Mctatrinitrobenzylamine  is  slightly  soluble  in  alcohol,  more 
readily  in  benzene,  and  forms  monoclmic  prisms,  melting  at 
162°.  It  does  not  combine  with  hydrochloric  acid. 

Metanitrobenzylplienylamine  is  formed  by  the  action  of  aniline 

1  Jackson  and  White,  Amer.  Chcm.  Journ.  ii.  317.  2  Ibid. 

3  Ber.  Dcutsch.  Chem.  Ges.  vi.  1056.     4  Borgruaim,  Chcm.  Centralb.  1885,  456. 


120  AROMATIC  COMPOUNDS. 

on  metanitrobenzyl  chloride.  The  hydrochloride,  which  is  thus 
obtained,  forms  small  white,  lustrous  plates.  It  is  decomposed 
by  water  with  formation  of  the  base,  which  crystallizes  in  long, 
orange-red  needles,  melting  at  86°. 

Amiddbenzylamines  are  obtained  by  the  reduction  of  the 
iiitro-compounds  with  tin  and  hydrochloric  acid. 

Paradiamidobenzylamine,  (C6H4(NH2)CH2)2NH,  is  readily 
soluble  in  hot  water  and  alcohol ;  it  crystallizes  in  needles  with  a 
satin  lustre,  or  in  plates  which  melt  at  106°,  and  volatilize  without 
decomposition  when  more  strongly  heated.  The  hydrochloride, 
(C6H4(NH3C1)CH2)2NH2C1,  is  readily  soluble  in  water,  slightly 
in  hydrochloric  acid,  and  crystallizes  in  small  white,  lustrous 
plates ;  the  platinichloride,  C14H18N3Cl.PtCl6,  forms  large  pointed 
reddish-yellow  needles  which  are  readily  soluble  in  water. 

Paratriamidobenzylamine,  (C6H4(NH2)CH2)3N,  is  insoluble  in 
water,  and  crystallizes  from  hot  alcohol  in  octahedra,  possessing 
a  diamond  lustre  and  melting  at  *  136°.  Its  hydrochloride 
crystallizes  in  yellow  needles,  and  is  so  readily  soluble  in  water, 
alcohol,  and  hydrochloric  acid,  that  it  cannot  be  obtained 
pure. 

In  the  preparation  of  the  base,  the  action  of  the  tin  and 
hydrochloric  acid  must  not  be  allowed  to  continue  too  long, 
as  under  these  circumstances  it  is  split  up  into  paradiamido- 
benzylamine  and  paratoluidine : 

/CH2.C6H4.NH2  CH2.C6H4.NH2 

Nf-CH0.C6H4.NH2+2H  =  HN<  +CH3.CrH4.NH2. 

\CH;C6H4.NH2  XCH2.C6H4.NH2 

Paramidobenzylphenylamine,  C6H4(NH2)CH2.N(C6H5)H,  can- 
not be  obtained  by  the  action  of  tin  and  hydrochloric  acid  on 
the  mtro-compoimd,  since  a  more  deeply  seated  decomposition 
takes  place;  the  reduction  may,  however,  be  effected  by 
employing  ammonium  sulphide.  The  base  is  soluble  in  water 
and  alcohol,  and  crystallizes  in  silky  scales,  which  melt  at  88° 
and  become  coloured  red  in  the  light. 

Metadiamidobenzylamine  forms  prismatic  needles,  melting  at 
86°;  its  hydrochloride,  (C6H4(NH3C1)CH2)2NH2C1,  crystallizes 
from  concentrated  hydrochloric  acid  in  long,  pinkish  needles,  and 
forms  a  readily  soluble  platinichloride. 

Metatriamidobenzylamine  forms  needles  melting  at  142°;  its 
platinichloride  is  only  slightly  soluble. 

Metamidobenzylphenylamine  melts  at  67°. 


BENZYLACETAMIDE.  121 


BENZYL-DERIVATIVES   OF  THE  ACID-AMIDES 
AND  ALLIED  BODIES. 

2080  Benzylacetamide,  C6H5.CH.2.N(C.2H30)H>  was  prepared 
by  Strakosch  by  heating  benzylamine  with  glacial  acetic  acid  for 
several  hours ; 1  it  is  more  readily  formed  by  the  action  of 
benzyl  chloride  on  acetamide,2  and*  is  very  soluble  in  alcohol  and 
ether,  slightly  in  petroleum  naphtha,  from  which  it  crystallizes 
in  small  plates,  which  have  a  pleasant  smell  of  flowers  and  melt 
at  57°.  It  boils  at  300°  and  is  not  attacked  by  acids  or 
aqueous  alkalis ;  alcoholic  potash,  however,  converts  it  into 
acetic  acid  and  benzylamine. 

Dibenzyloxamide,  (C6H5.CH2.NH2)2C2O2,  is  obtained  by  boiling 
benzylamine  with  ethyl  oxalate ;  it  is  insoluble  in  water,  slightly 
soluble  in  hot  alcohol,  from  which  it  crystallizes  in  scales,  which 
possess  a  satin  lustre  and  melt  at  216°. 

Cyanobenzylamine,  C18H16N4,  is  obtained  by  passing  cyanogen 
into  a  cold  solution  of  benzylamine : 

C6H5.CH2.NH2        C=N        C6H5.CH2.NH.C=NH 

+    I  I 

C6H5.CH2.NH2        C=N        C6H5.CH2.NH.C=NH. 

It  forms  lustrous  crystals,  which  are  soluble  in  alcohol  and 
melt  at  140°.  If  hydrochloric  acid  be  added  to  the  alcoholic 
solution,  the  salt,  C18H16N4(C1H)2,  is  obtained  in  white,  silky 
needles.  When  it  is  allowed  to  stand  in  contact  with  hydro- 
chleric  acid  for  some  time,  it  is  converted  into  dibenzyloxamide 
(Strakosch). 

Benzykyanamide,  C6H5.CH2.NH(CN),  is  formed  when  cyan- 
ogen chloride  is  passed  into  an  ethereal  solution  of  benzyl- 
amine, and  crystallizes  in  tablets  melting  at  33°.  It  changes 
spontaneously  into  ~benzy  Icy  anur  amide  or  lenzylmelamine,  (C6H5. 
CH2.NH)3C3N3,  which  has  a  much  higher  melting-point  and 
crystallizes  from  alcohol  in  plates ;  the  change  takes  place  more 
readily  at  100°. 

When  an  alcoholic  solution  of  benzylcyanamide  is  boiled  with 
benzylamine  hydrochloride,  dibenzyl guanidine  (C6H5.CH2.NH)2 
C.NH,  is  formed ;  this  compound  crystallizes  from  alcohol  in 

1  Ber.  Deutsch.  Chem.  Ges.  v.  697. 

2  Rudolph,  ibid.  xii.  1297. 


122  AROMATIC  COMPOUNDS. 

plates  or  tablets,  melting  at  100°.  The  hydrochloride,  (C7H7. 
NH)2C.NH.C1H,  is  slightly  soluble  in  water,  more  readily  in 
alcohol  (Strakosch). 

Dibenzylcyanamide,  (C6H5.CH2)2N.CN,  was  obtained  by  Lim- 
pricht  from  dibenzylamine  and  cyanogen  chloride ;  it  crystallizes 
from  alcohol  in  plates,  melting  at  53° — 54°. 

Benzyl  isocyanate,  or  Benzyl  carbimide,  C6H5.CH0N  :  CO,  was 
prepared  by  Letts  in  the  impure  state  and  in  small  quantity, 
by  distilling  benzyl  chloride  with  silver  cyanate  ;l  the  isocyanurate 
is  always  formed  at  the  same  time.  It  is  a  liquid  which  gives 
all  the  characteristic  reactions  of  the  isocyanates  and  possesses 
an  extremely  penetrating  odour,  its  vapour  attacking  the  eyes 
violently. 

Benzyl  isocyanurate,  (C6H5.CH2)3N3(CO)3,  crystallizes  from  hot 
alcohol  in  silky  needles,  melting  at  157°.  It  boils  above  320°,  and 
when  fused  with  caustic  potash  yields  benzylamine.  Cannizzaro 
seems  to  have  obtained  the  same  substance  in  small  quantity 
and  together  with  other  products  by  the  action  of  cyanuric 
chloride  on  benzyl  alcohol.2 

Benzyl  isothiocyanate,  or  Benzyl  mustard  oil,  C6H5.CH2.N:CS. 
Hofmann  obtained  this  compound  by  dissolving  benzylamine  in 
carbon  disulphide,  and  distilling  the  white,  crystalline  compound 
formed  with  an  alcoholic  solution  of  mercuric  chloride 3 

It  is  a  liquid  which  boils  at  about  243°  and  possesses  the  smell 
of  water-cress  (Nasturtium  officinale)  in  such  a  remarkable 
degree  that  Hofmann  was  induced  to  search  for  it  in  the  oil  of 
this  plant ;  it  is  not,  however,  present,  the  odoriferous  constituent 
in  water-cress  being  phenylpropionitril,  C6H5.C2H4.CN,4  w,hile 
benzonitril,  C6H5CN,  is  that  of  the  nasturtium  (Tropaeolum 
majuslf 

Benzyl  tkiocyanate,  C6H5.CH2.S.CN,  is  formed  by  heating 
benzyl  chloride  with  an  alcoholic  solution  of  potassium  thio- 
cyanate.  It  is  insoluble  in  water,  and  crystallizes  from  alcohol  in 
long,  transparent  prisms,  which  have  a  sharp,  burning  taste,  and 
a  penetrating  smell  resembling  that  of  cress.  According  to 
Henry,6  it  melts  at  36° — 38°  and  boils  with  partial  decomposition 
at  256°,  while  Barbaglia  found  its  melting-point  to  be  41°  and 
its  boiling-point  230°— 2350.7 

1  J3er.  Deutsch.  Chem.  Ges.  v.  90  ;  see  also  Strakosch,  ibid,  v,  692  ;  Ladenburg, 
ibid.  x.  46. 

2  Ber.  Deutsch.  Chcm.  Ges.  iii.  517.  3  Ibid.  i.  201. 
4  Ibid.  vii.  520.                  6  Ibid.  vii.  518.  6  Ibid.  ii.  638. 
7  Ibid.  v.  688. 


BENZYL  UREAS.  123 


Concentrated  nitric  acid  converts  it  into  paranitrobenzyl  thio- 
cyanate,  C6H4(N02)CH2.S.CN,  which  can  also  be  obtained  by 
the  action  of  paranitrobenzyl  chloride  on  potassium  thiocyanate. 
It  crystallizes  from  alcoholic  solution  in  small,  brittle  crystals. 

Various  halogen  substitution-products  of  this  compound  are 
also  known.1 

Benzyl  selenocyanate^^^.GYL^Q. ON,  crystallizes  from  alcohol 
in  white  needles  or  prisms,  which  have  an  extremely  repulsive 
smell  and  melt  at  7l'5°.2 

Benzyl  carbamate,  or  Benzyl  urethane,  C6H5.CH2.O.CO.NH2, 
was  obtained  by  Cannizzaro,  together  with  a  little  benzyl 
isocyanurate  and  dibenzyl  urea,  by  the  action  of  cyanogen 
chloride  and  cyanuric  chloride  on  benzyl  alcohol.3  It  is  also 
formed  when  urea  nitrate  is  heated  to  130° — 140°4  with  benzyl 
alcohol;  it  crystallizes  from  hot  water  in  large  plates,  which 
melt  at  86°  and  decompose  into  benzyl  alcohol  and  cyanuric  acid 
at  220°. 

Benzyl  urea,  (C6H5.CH2)NH  CO.NH2,  is  formed,  together  with 
symmetric  dibenzyl  urea,  by  the  action  of  benzyl  chloride  on  an 
alcoholic  solution  of  potassium  cyanate,5  as  well  as  by  that  of 
alcoholic  ammonia  on  benzyl  isocyanate  (Letts).  It  is  also 
obtained  when  a  solution  of  benzylamine  hydrochloride  is  boiled 
with  potassium  cyanate.6  It  is  tolerably  soluble  in  hot,  readily 
in  boiling  alcohol,  and  crystallizes  in  long,  white  needles,  melting 
at  147°— 147-5°. 

Symmetric  dibenzyl  urea,  CO(NH.CH2.C6H5)2,  is  formed  when 
the  compound  just  described  is  heated  to  200°  (Cannizzaro),  as 
well  as  when  benzyl  isocyanate  is  heated  with  water  in  a  sealed 
tube  to  100°,  and  also  when  benzyl  alcohol  is  heated  to  100° 
with  urea  nitrate  (Letts),  benzylaldehyde  being  simultaneously 
formed  (Campisi  and  Amato).  It  is  insoluble  in  water  and 
crystallizes  from  alcohol  in  needles  melting  at  167°.  It  does 
not  combine  with  hydrochloric  acid  or  nitric  acid,  but  gives  a 
plantinichloride. 

Asymmetric  dibenzyl  urea,  (C6H5.CH2)2N.CO.NH2,  has  been 
obtained  by  Paterno  and  Spica  from  dibenzylamine  hydrochloride 
and  potassium  cyanate ;  it  is  slightly  soluble  in  cold,  readily  in 
hot  water,  and  crystallizes  in  thick  prisms,  melting  at  124° — 125°. 

1  Jackson,  Field,  Mabery,  Lowry,   loc.  cit. 

2  Jackson,  Ann.  Chem.  Pharm.  clxxix.  15. 

3  Ber.  Dcutsch.  CJiem.  Ges.  iii.  517  ;  iv.  412. 

4  Campisi  and  Amato,  ibid.  iv.  412. 

6  Patemo  and  Spica,  ibid.  ix.  81.  8  Ibid. 


124  AROMATIC  COMPOUNDS. 

Benzyl  tJiiocarbamide ,  C6H5.CH2.NH.CS.NH2,has  been  prepared 
in  an  analogous  manner  from  benzylamine  hydrochloride  and 
potassium  thiocyanate ;  it  is  very  soluble  in  water  and  melts  at 
101°. 

Symmetric  dibenzyl  thiocarbamide,  (C6H5.CH2.NH)9CS,  is 
formed  when  an  alcoholic  solution  of  benzylamine  is  heated  with 
carbon  disulphide  until  the  evolution  of  sulphuretted  hydrogen 
ceases.  It  crystallizes  in  large,  four-sided,  lustrous  tablets,  melt- 
ing at  114° ;  it  is  converted  into  dibenzyl  urea  when  its  alcoholic 
solution  is  treated  with  mercuric  oxide  (Strakosch). 

Asymmetric  dibenzyl  thiocarbamide,  (C6H5.CH9N)2CS.NH0,  is 
prepared  from  dibenzylamine  hydrochloride  and  potassium 
thiocyanate ;  it  is  slightly  soluble  in  water,  readily  in  alcohol, 
and  crystallizes  in  long  needles  melting  at  156° — 157°  (Paterno 
and  Spica). 


PHOSPHORUS   COMPOUNDS   OF   BENZYL. 

2081  Primary  and  secondary  benzylphosphine  are  formed 
when  benzyl  chloride  is  heated  with  phosphonium  iodide  and  zinc 
oxide.  The  product  of  the  reaction  is  distilled  with  water,  an 
oily  liquid  coming  over,  which  possesses  a  very  characteristic, 
persistent  odour,  and  is  a  mixture  of  toluene  and  benzylphos- 
phine. The  residue  contains  dibenzylphosphine  and  other 
substances,  which,  however,  remain  in  solution,  while  the 
dibenzylphosphine  crystallizes  out  on  standing,  more  rapidly  in 
the  presence  of  caustic  potash  ;  it  is  then  removed  from  the 
liquid  and  recryst  alii  zed  from  boiling  alcohol.1 

Benzylphosphine,  C6H5.CH2.PH2,  is  a  strongly  refractive  liquid, 
boiling  at  180° ;  it  is  oxidized  on  exposure  to  the  air  with  such 
rapidity  that  its  temperature  rises  to  above  100°,  thick,  white 
needles  being  deposited. 

Benzyl phosplionium  iodide,  C6H5.CH2.PH3I,  is  obtained  by  the 
addition  of  fuming  hydriodic  acid  to  benzylphosphine,  as  a  white 
precipitate  which  crystallizes  from  the  hot  acid  in  long,  white 
needles.  When  these  are  washed  with  ether  and  dried  in  a 
stream  of  hydrogen,  they  are  converted  into  large,  well-formed 
tablets.  Water  decomposes  the  compound  into  its  constituents. 

1  Hofmann,  Bcr.  Dcutsch.  Chem.  Gc\  v.  100. 


ARSENIC  COMPOUNDS  OF  BENZYL.  125 

1      •  '  *    •  -— "•  —          -•• —  •  •  —  • 

Dibenzylphosphine,    (C6H5CH2)2PH,    crystallizes    in    needles 
rhich  form  star-like  aggregates,  are  colourless  and  tasteless,  do 
>t  combine  with  acids,  and  melt  at   205°.     While  dimethyl- 
losphine  and  ethylphosphine  are  spontaneously  inflammable  in 
air,  dibenzylphosphine  is  not  acted  upon  by  oxygen,  even 
a  higher  temperature. 

Triphenylbenzylphosphonium  chloride,   P(C6H5)3(CH2.C6H5) Cl, 
readily  formed  by  the    combination  of  benzylchloride  with 
iphenylphosphine.      It  is  readily  soluble  in  alcohol  and  water, 
id  separates  from  the  latter  in  rhombic  crystals  which  contain 
molecule  of  water  and  are  efflorescent.     Other  salts,  which 
characterized  by  their  power  of   crystallization,  have  been 
spared  from  this  compound  by  double  decomposition ;  they  are 
lecomposed  by  boiling  caustic  soda,  with  formation  of  triphenyl- 
losphine  oxide  and  toluene  : l 


ARSENIC   COMPOUNDS   OF   BENZYL. 

2082  When  benzyl  chloride,  diluted  with  absolute  ether,  is 
ited  with  arsenic  trichloride  and  sodium,  a  reaction  commences 
ir  some  time,  which  in  the  course  of  a  few  days  may  raise  the 

jmperature  to  the  boiling-point  of  ether,  the  following  com- 

mnds  being  formed  : 

Dibenzylarsine  trichloride. 

2C7H7C1 + AsCl3 + 2Na  =  (C7H7)2AsCl3 + 2N  aCl. 

Tribenzylarsine  di chloride. 

3C7H7C1  +  AsCl3  +  4Na=  (C7H7)3AsCl2  +  4NaCl. 

If  the  sodium  chloride  be  now  removed,  the  ether  distilled  off 
id  the  residue  treated  with  ordinary  ether  containing  water, 
le  chlorides  are  converted  into  oxychlorides,  which  separate  out 
a  powder,  while  resinous  by-products  containing  arsenic  go 
ito  solution.    The  powder  is  washed  with  ether  and  then  treated 
ith  boiling  dilute  caustic  soda  solution ;  dibenzylarsenic  acid 
into  solution,  while  the  residue  consists  of  tribenzylarsine 
>xide,  which  is  very  slightly  soluble  in  the  cold  solution,  and  is, 
therefore,  removed  by  cooling  and  filtering. 

1  Michaelis  and  V.  Soden,  Ann.  Chcm.  Pharm.  ccxxix.  319. 


126  AKOMATIC  COMPOUNDS, 

Dibenzylarsenic  acid,  (C6H5.CH2)2AsO.OH,  is  precipitated  from 
its  alkaline  solution  by  acids ;  it  is  only  very  slightly  soluble  in 
cold,  more  readily  in  boiling  water,  and  crystallizes  from  hot 
dilute  alcohol  in  fine,  white  plates,  melting  at  210'5°.  It  dissolves 
in  hot  dilute  hydrochloric  acid  and  the  solution  on  cooling 
deposits  the  compound  (C7H7)2As(OH)2Cl,  in  fine  needles,  which 
melt  at  128°  and  are  reconverted  into  the  acid  by  water.  It 
forms  similar  compounds  with  hydrobromic,  hydriodic  and  nitric 
acids.  It  is  decomposed  on  heating  with  concentrated  hydro- 
chloric acid : 

2(C7H7)2As02H  +  2HC1  =  2C7H7C1  +  2C7H8  +  As2O3  +  H20. 

It  behaves  in  this  reaction  similarly  to  cacodylic  or  di- 
methylarsenic  acid.  Its  alkaline  salts  are  soluble  in  water  and 
alcohol;  those  of  the  calcium  group  separate  from  alcohol  in 
crystals ;  the  silver  salt  is  a  white  precipitate,  insoluble  in  water. 

Tribenzylarsine  oxide,  (C6H5.CH2)3AsO,  crystallizes  from  dilute 
alcohol  in  lustrous  needles,  melting  at  219'5°.  On  heating  with 
hydrochloric  acid  it  is  converted  into  the  oxychloride,  (C7H7)3 
As(OH)Cl,  which  melts  at  162°— 163°  and  is  reconverted  into 
the  oxide  by  alkalis. 

Tribenzylarsine,  (C6H5CH2)3As.  When  a  little  acetic  ether  is 
added  to  the  mixture  employed  in  the  preparation  of  the 
compounds  just  described,  the  reaction  becomes  so  violent  that 
it  has  to  be  moderated  by  cooling  : 

3C7H7C1  +  AsCl3  +  6Na  =  (C7H7)3As  +  GNaCl. 

If  the  treatment  described  above  be  then  proceeded  with,  the 
oxychlorides  are  obtained  as  before,  but  the  solution  contains 
tribenzylarsine  and  no  resinous  by-products ;  it  crystallizes  from 
alcohol  in  large  colourless  needles,  melting  at  104°.  On  heating 
with  ethyl  iodide,  tribenzylarsonium  iodide,  (C6H5.CH2)3C2H5 Asl, 
is  formed,  and  crystallizes  in  small  white  plates,  which  are 
slightly  soluble  in  water,  readily  in  alcohol.1 

Tribenzylarsine  is  isomeric  with  tritolylarsine,  (C6H4.CH3)3As, 
which,  like  triphenylarsine,  forms  no  compounds  with  the 
alcoholic  iodides. 

1  Michaelis  and  Paetow,  Ber.  Deutsch.  Chem.  Ges.  xviii.  41. 


SILICON  TETKABENZYL. 


127 


SILICON    COMPOUNDS   OF   BENZYL. 

2083  Silicon  tetrabenzyl,  or  Silieotetrdbenzylmethane,  Si(CH2. 
;CH5)4,  is  formed  by  the  action  of  sodium  on  a  mixture  of 
jnzylchloride  and  silicon  chloride,  to  which  a  little  acetic  ether 
been  added,  and  which  has  been  diluted  with  ether.  It 
?parates  fiom  warm  ether  in  crystals  melting  at 

1  Polls,  Ber.  Deutsch.  Chem.  Ges.  xviii.  1543. 


128  AROMATIC  COMPOUNDS. 


THE  BENZOYL  GROUP. 

2084  It  has  been  already  mentioned  in  the  introductory  sketch 
of  the  development  of  organic  chemistry  (Part  I.  p.  11),  that 
Wohler  and  Liebig  showed  in  their  classical  research,  Investiga- 
tions on  the  Radical  of  Benzoic  Acid,  that  oil  of  bitter  almonds, 
benzoic  acid,  and  a  number  of  substances  prepared  from  these,  all 
contain  a  "compound  basis  "  of  the  formula  C7H5O,  to  which  they 
gave  the  name  of  benzoyl  (the  latter  portion  of  the  word  being 
derived  from  v\7j,  matter).1  They  communicated  their  results 
to  Berzelius,  who  makes  the  following  remarks  in  his  reply : 

"  The  results  which  you  have  obtained  by  the  investigation  of 
oil  of  bitter  almonds,  are  certainly  the  most  important  which 
have  hitherto  been  attained  in  the  field  of  vegetable  chemistry, 
and  promise  to  throw  an  unexpected  light  upon  that  department 
of  science.  The  fact  that  a  substance  which  is  composed  of  carbon, 
hydrogen  and  oxygen,  combines  with  other  substances,  but 
especially  with  those  which  form  salts  and  bases,  in  precisely  the 
same  manner  as  do  simple  substances,  proves  that  there  are 
ternary  compound  atoms  (of  the  first  order),  and  the  radical  of 
benzoic  acid  is  the  first  well-established  instance  of  a  ternary 
substance  which  possesses  the  properties  of  an  element. 

"  The  facts  brought  forward  by  you  give  rise  to  such  wide 
considerations  that  they  may  be  looked  upon  as  marking  the 
commencement  of  a  new  era  in  vegetable  chemistry.  From  this 
standpoint  I  should  propose  to  name  the  first  discovered  radical 
composed  of  more  than  two  elements,  proin  (from  the  word 
commencement  of  the  day,  in  the  sense,  CLTTO  Trpwl  eo>? 
Acts  xxviii.  23),  or  orthrin  (from  6p(p>p6?,  dawn.)" 

In  view,  however,  of  the  circumstance  that  the  long  familiar 
name  benzoic  acid  would  have  also  been  altered,  and  that  it  is 
customary  to  respect  terms  in  general  use,  provided  only  that 

1  Ann.  Chem.  Pharm.  iii.  249. 


BEXZALDEHYDE. 

they  do  not  admit  of  a  double  interpretation,  it  seemed  to  him 
most  suitable  to  accept  the  name  benzoyl.1 

In  the  next  year,  nevertheless,  he  opposed  the  idea  of  the 
existence  of  oxygenated  radicals  and  looked  upon  oil  of  bitter 
almonds  as  an  oxide  of  picramyl,  C7H6  (in/epos,  bitter,  and 
,  almond),  a  name  which  was  never  generally  adopted. 


BENZALDEHYDE,  C6H5.CHO. 

2085  The  poisonous  qualities  of  bitter  almonds  were  known 
to  the  ancients,  and  they  were  employed  in  medicine  in  the 
middle  ages :  Valerius  Cordus,  who  has  been  already  mentioned 
under  the  history  of  ether,  described  them  as  constituents  of 
lozenges.  At  the  commencement  of  this  century,  Bohm,  an 
apothecary's  assistant  in  Berlin,  discovered  that  the  aqueous 
distillate  of  bitter  almonds  contains  prussic  acid,2  and  this  dis- 
covery led  to  the  assumption  that  the  latter  is  poisonous,  a 
property  which  its  discoverer,  Scheele,  had,  somewhat  strangely, 
overlooked.  Schaub,  Schrader,  Ittner  and  other  chemists3 
confirmed  the  dangerous  nature  of  this  substance,  and  Schrader,4 
and  Matres,5  an  apothecary  in  Montauban,  observed  that  a  liquid  oil 
is  also  obtained  by  the  distillation  of  bitter  almonds  with  water. 
This  oil  was  more  closely  examined  by  Vogel  and  Robiquet, 
the  former0  of  whom  found  that  the  most  remarkable  and 
striking  property  of  oil  of  bitter  almonds  is  that  it  is  converted 
into  a  crystalline  body  by  exposure  to  the  air  or  by  treat- 
ment with  pure  oxygen  or  oxy muriatic  acid  (chlorine),  while 
Robiquet  showed  that  the  leaves  of  the  cherry-laurel  yield  an 
oil  which  resembles  oil  of  bitter  almonds  in  every  respect,  and 
that  the  substance  obtained  from  it  by  oxidation  has  acid  pro- 
perties.7 

Stange,  an  apothecary  of  Basel,  who  also  obtained  this  solid 
substance  from  the  cherry-laurel,  recognized  it  as  benzoic  acid,8  an 

1  Ann.  Chem.  Pharm.  iii.  282. 

-  Scherer's  Journ.  x.  126  ;  Gilbert,  Ann.  Phys.  xiii.  503. 

3  Ittner,  Bcitrdge  zur  Geschichte  dcr  Blamaure,  Freiburg  and  Constanz,  1809  ; 
Preyer,  Die  Blausaure,  Bonn,  1870,  154. 

4  Schrader,  Berlin.  Jahrb.  Pharm.  ii.  43. 

5  Journ.  Pharm.  v.  289. 

6  Schweigger,  Journ.  Chem.  Phy*.  xx.  59  ;  xxxii.  119. 
r  Ann.  Chim.  Phys.  xv.  29  ;  xxi.  250. 

8  Buclmer'.s  Rcpert.  Pharm.  xiv.  329,  361  ;  xvi.  80. 


130  AKOMATIC  COMPOUNDS. 

observation  which  was  confirmed  by  Wohler  and  Liebig.  These 
chemists  determined  its  composition,  and  that  of  the  oil  of 
bitter  almonds,  and  ascertained  the  relations  of  the  two  com- 
pounds. To  oil  of  bitter  almonds  they  gave  the  name  of  benzoyl 
hydride,  which  was  later  changed  to  benzoic  aldehyde  and 
benzaldehyde. 

Shortly  before  this,  Robiquet  and  Boutron-Charlard  had 
found  that  when  bitter  almonds  are  freed  from  fatty  matters 
by  pressure,  an  odourless  residue  is  left  which  yields  the 
characteristic  smell  of  oil  of  bitter  almonds  on  the  addition 
of  water.  The  oil  in  question,  or  its  elements,  had  there- 
fore been  left  behind  in  the  pressed  mass  and  had  not  been 
removed  by  the  process.  They,  therefore,  concluded  that  oil  of 
bitter  almonds  is  a  compound  of  water  with  a  peculiar  principle, 
which  they  endeavoured  to  isolate.  The  use  of  water  being 
impossible,  they  extracted  the  pressed  almonds  with  boiling 
alcohol,  and  obtained,  together  with  resin  and  a  liquid  sugar,  a 
crystalline  compound  containing  nitrogen,  to  which  they  gave 
the  name  of  amygdalin.  This  compound,  to  which  the  taste  of 
bitter  almonds  is  due,  gave  .no  smell  of  bitter  almonds  when 
treated  with  water,  nor  did  either  of  the  two  other  compounds, 
nor  the  residue,  nor  even  of  a  mixture  of  them  all.  The  prussic 
acid  and  oil  of  bitter  almonds  had  vanished  from  their  hands.1 
They  found  further,  that  sweet  almonds  contain  no  amygdalin 
and  that  the  latter  yields  benzoic  acid  when  oxidized  by  nitric 
acid,  while  Peligot  observed  the  formation  of  oil  of  bitter  almonds 
as  an  intermediate  product  in  this  reaction. 

Wohler  and  Liebig,  who  also  accurately  determined  the 
composition  of  amygdalin,  succeeded  in  finding  the  solution  of 
the  problem.  They  showed  that  both  sweet  and  bitter  almonds 
contain  a  peculiar  nitrogenous  substance,  emulsin,  which  con- 
verts amygdalin  in  presence  of  water  into  benzaldehyde,  prussic 
acid,  and  grape  sugar  • 

C20H27NOU  +  2H20  =  C7H60  *  CNH  +  2C6H1206. 

The  action  of  the  ferment  is  destroyed  by  boiling  water  and  by 
heating  with  alcohol,  so  that  when  dried  and  powdered  bitter 
almonds  are  shaken  up  with  boiling  water  and  distilled,  none  of 
the  liquid  oil  is  obtained,  and  the  same  result  occurs  when,  as  in 

1  Ann.  Chim.  Phys.  xliv.  352. 


OCCURRENCE  OF  BENZALDEHYDE.         131 



Robiquet  and  Boutron-Charlard's  process,  they  are  treated  with 
boiling  alcohol.1 

Amygdalin,  which  is  the  first  example  of  a  glucoside,  a  large 
number  of  which  bodies  is  now  known,  occurs  in  many  plants, 
chiefly  the  Amygdalacece,  Drupacece  and  Pomacece,  which  all 
yield  benzaldehyde  and  prussic  acid  when  distilled  with  water. 
The  kernel  of  the  peach  also  yields  an  oil  resembling  oil  of 
bitter  almonds  in  every  respect,2  while  that  obtained  from  the 
leaves,  flowers,  seeds  and  bark  of  the  cherry,  contains  both  oil  of 
bitter  almonds  and  another  oil  which  has  a  penetrating,  repul- 
sive odour.3  This  subject  will  be  further  discussed  under 
Amygdalin. 

According  to  Winkler,  the  fresh  leaves  of  the  cherry-laurel 
(Prunus  laurocerams),  the  cherry  (Prunus  padus)  and  the  peach, 
contain  a  small  quantity  of  free  oil  of  bitter  almonds  varying  in 
amount  with  the  water  present,4  which  can  be  extracted  by  ether. 

Ittner  looked  upon  oil  of  bitter  almonds  as  a  compound  of 
hydrocyanic  acid  and  an  ethereal  oil,  but  \Togel  opposed  this 
view,  for  he  had  found  that  it  could  be  easily  freed  from  hydro- 
cyanic acid  by  treatment  with  caustic  potash  or  baryta  water,  or 
by  distillation  with  mercuric  oxide.5  Since,  however,  the  oil 
containing  hydrocyanic  acid  is  readily  converted  into  the  polymeric 
benzoin,  C14H12O2,  by  caustic  potash,  Wohler  and  Liebig  proposed 
to  remove  the  acid  by  shaking  up  with  milk  of  lime  and  ferrous 
sulphate,  calcium  ferrocyanide  being  formed  ;  a  loss  of  about  1 0 
per  cent,  is  experienced  in  the  process.  According  to  Bertagnini 
it  is  better  to  shake  the  oil  with  three  or  four  volumes  of  acid 
sodium  sulphite,  remove  the  crystals  which  separate  out  and 
wash  with  alcohol.6  All  the  hydrocyanic  acid  is  not  removed 
by  this  process,  and  the  double  sulphite  is  therefore  recrystal- 
lized  from  hot  alcohol  before  being  distilled  with  caustic  soda.7 
The  oil  containing  hydrocyanic  acid  is  not  simply  a  mixture  of 
benzaldehyde  and  hydrocyanic  acid,  but  contains  phenylhydroxy- 
acetonitril,  C6H5.CH(OH)CN,  which,  like  other  cyanhydrins  or 
nitrils  of  hydroxyacids,  readily  decomposes  into  its  constituents. 
Winkler  had  noticed  some  time  previously  that  crude  oil  of  bitter 
almonds  is  converted  by  hydrochloric  acid  into  mandelic  acid 

1  Ann.  Chem.  Pharm.  xxii.  1  ;  Robiquet  and  Boutron,  ibid.  xxv.  175  ;  Liebig, 
ibid.  xxv.  190. 

2  Righini,  ibid.  x.  359  ;  Geissler,  ibid,  xxxvi.  331. 

3  Winkler,  Repcrt.  Pharm.  Ixvii.  1,  56. 

4  Jahresb.  Chem.  iv.  519.  6  Loc.  cit.  ;  Ittner,  ibid.  xxiv.  395. 

6  Ann.  Chem.  Pharm.  Ixxxv.  183.          7  Muller  and  Limpricht,  ibid.  cxi.  136. 


132  AKOMATIC  COMPOUNDS. 

or plienylhydroxy 'acetic  acid,  CCH5.CH(OH)C02H,  the  formation  of 
which,  however,  cannot  be  taken  as  a  proof  of  the  presence  of  the 
nitril,  for  this  acid  is  also  formed  when  a  mixture  of  hydrochloric 
acid,  hydrocyanic  acid  and  benzaldehyde,  is  heated  to  boiling. 
Fileti,  however,  supplied  the  proof  by  showing  that  phenyl- 
ethylamine,  C6H5.CH2.CH2.NH2,  is  formed  by  the  action  of  zinc 
and  hydrochloric  acid  on  an  alcoholic  solution  of  crude  oil  of 
bitter  almonds  or  of  the  cherry-laurel,  while  a  mixture  of  benz- 
aldehyde and  hydrocyanic  acid  subjected  to  the  same  treatment 
yielded  methylamine.1 

2086  Oil  of  bitter  almonds  is  prepared  on  the  large  scale  by 
distilling  the  pressed  residue  of  bitter  almonds  with  water.  In 
order  to  get  all  the  amygdalin  into  solution  and  obtain  the 
best  yield  of  oil,  Pettenhofer  brings  12  parts  of  the  roughly 
powdered  mass  into  100 — 120  parts  of  boiling  water,  keeps  it  at 
the  boiling-point  for  15 — 30  minutes,  and  after  cooling  adds  1 
part  of  the  powder  stirred  up  with  6 — 7  parts  of  water,  and 
then  rapidly  distils.2  The  aqueous  distillate  contains  some  oil  in 
solution,  which  is  removed  by  a  subsequent  distillation. 

Pettenhofer  obtains  a  yield  of  0*9  per  cent,  of  oil  of  bitter 
almonds  on  the  pressed  residue,  while  on  the  large  scale  the 
yield  is  in  this  way  074 — 1'67  per  cent,  or  0*42 — 0'95  parts  in 
100  of  bitter  almonds.  The  great  variation  in  these  numbers  is 
partly  accounted  for  by  the  varying  amounts  of  amygdalin 
present,  but  is  also  due  to  the  admixture  of  sweet  almonds.3 

Some  manufacturers  free  the  oil  from  hydrocyanic  acid ;  the 
purified  oil,  however,  oxidizes  much  more  readily  than  when  in 
the  crude  state,  so  that  others  add  hydrocyanic  acid  and  warm 
gently4  in  order  to  make  it  keep  better,  the  nitril,  which  will  be 
described  under  Phenylhydroxyacetic  acid,  being  formed. 

Oil  of  bitter  almonds  is  chiefly  employed  in  perfumery,  and 
as  a  flavouring,  for  which,  however,  it  must  be  used  with  care. 
Extracts  of  bitter  almonds  and  of  cherry-laurel  are  used  in 
medicine. 

Benzaldehyde  can  be  obtained  in  many  other  ways,  some  of 
which  have  been  already  mentioned  under  the  benzyl  com- 
pounds. Dumas  and  Peligot  obtained  it  by  oxidation  of  cinnamic 
acid,  CGH5.CH=CH.C02H;5  Muller  prepared  it  in  a  similar 

1  (7az.  Chim.  Itnl.  viii.  446.  2  Ann.  Chem..  Pharm.  cxxii.  77. 

3  Fliickiger  and  Hanbury,  Pharmncographia,  2nd  ed.  250. 

4  'Dustat,  Bull,  fine.  Chim.  [2]  viii.  459. 

5  Ann.  Chem.  Pharm.  xiv.  385. 


PREPARATION  OF  BENZALDEHYDE.        133 

manner  from  oil  of  cinnamon,  which  contains  cinnyl  alde- 
hyde,1 arid  Toel  from  styrone  or  cinnyl  alcohol,  C6H5.CH= 
CH.CH2.OH.2  Various  other  allied  aromatic  compounds  yield 
benzaldehyde  on  oxidation.  Cannizzaro  showed  that  it  is  the 
first  product  of  the  oxidation  of  benzyl  alcohol  (p.  91),  while 
Guckelberger  and  Keller  found  it  among  the  products  which  are 
formed  by  the  action  of  potassium  permanganate  and  sulphuric 
acid  on  the  albuminoids.3 

It  is  readily  obtained  from  benzoic  acid  by  reduction  carried 
on  in  -aqueous  solution  by  means  of  sodium  amalgam,4  or  by 
heating  with  stannous  oxide.5  Baeyer  obtained  it  by  passing 
the  vapour  of  benzoic  acid  or  of  phthalic  acid,  C6H4(C02H)2,  over 
heated  zinc-dust 6  and  Chiozza  by  the  action  of  copper  hydride 
on  benzoyl  chloride.7  Piria  found  that  it  is  formed  by  distilling 
a  mixture  of  calcium  benzoate  and  formate.8 

When  the  vapour  of  benzene  or  toluene,  mixed  with  air,  is 
brought  into  contact  with  a  glowing  spiral  of  platinum  or  palla- 
dium, benzoic  acid  is  formed  together  with  some  benzaldehyde, 
which  is  formed  in  larger  quantity  from  xylene  (dimethylbenzene) 
or  cymene  (methylpropylbenzene.)9  Toluene,  as  already  men- 
tioned (p.  6),  forms  a  compound  with  chromium  oxychloride, 
which  is  decomposed  by  water  with  formation  of  benzaldehyde. 

This  is  also  formed  when  benzyl  chloride  is  boiled  with  dilute 
nitric  acid  or  water  and  lead  nitrate,10  as  well  as  by  heating 
benzidene  chloride,  C6H5.CHC12,  with  silver  oxide,  mercuric 
oxide,11  or  alcoholic  potash,12  or  with  water  to  140°— 1600.13  When 
this  compound  is  heated  with  two  molecules  of  sulphuric  acid 
to  30°,  hydrochloric  acid  is  evolved  and  a  syrupy  liquid  formed, 
which  is  decomposed  by  water  into  sulphuric  acid  and  benz- 
aldehyde.14 

On  the  small  scale  benzaldehyde  is  best  prepared  by  gradually 
heating  benzidene  chloride  to  130°  with  the  necessary  amount 
of  anhydrous  oxalic  acid  : 

C6H5.CHC12  +  C2H2O4  =  C6H5.CHO  +  CO  +  CO2  +  2HC1. 

1  Journ.  Prakt.  Chem.  xviii.  385.  2  Ann.  Chem.  Pharm.  Ixx.  5. 

3  Ibid.  Ixiv.  60  ;  Ixxii.  86.  *  Kolbe,  ibid,  cxviii.  122. 

5  Dusart,  Compt.  Rend.  Iv.  448.  6  Ann.  Chem.  Pharm.  crl.  296. 

7  ibid.  Ixxxv.  232.  8  Ibid.  c.  105. 

9  Coquillon,  Compt.  Rend.  Ixxvii.  444  ;  Ixxx.  1089. 
10  Grimaux  and  Lauth,  Bull.  Soc.  Chim.  [2]  vii.  106. 
^  Gerhardt,  Traite  Chim.  iv.  721. 

12  Cahours,  Ann.  Chem.  Pharm.  Suppl.  ii.  253. 

13  Limpricht,  ibid,  cxxxix.  319. 

14  Oppenheim,  Ber.  Dcutsch.  Chem.  Ges.  ii.  213. 

240 


134  AROMATIC  COMPOUNDS. 

The  residue  is  distilled  under  diminished  pressure,  and  the 
aldehyde  purified  by  a  single  rectification.1 

2087  Benzaldehyde  is  manufactured  by  boiling  2  parts  of 
benzyl  chloride  with  3  parts  of  lead  nitrate,  or  better,  copper 
nitrate,  and  10  parts  of  water  for  several  hours  in  an  apparatus 
connected  with  an  inverted  condenser,  the  operation  being 
conducted  in  a  current  of  carbon  dioxide ;  half  the  liquid 
is  then  distilled  off,  and  the  oil  separated  from  the  water. 
It  is  obtained  from  benzidene  chloride  by  heating  it  under 
pressure  in  an  iron  vessel  with  caustic  soda.  According 
to  Espenschied  it  is  possible  to  heat  without  pressure  in  an 
apparatus  connected  with  an  inverted  condenser  if  milk  of  lime 
be  used,  or  if  whitening,  or  some  other  finely-divided  insoluble 
substance,  be  added  and  the  whole  stirred  into  an  emulsion, 
which  boils  at  a  higher  temperature  and  thus  facilitates  the 
decomposition  of  the  chloride.  Jacobsen  recommends  a  process 
in  which  benzidene  chloride  is  heated  with  glacial  acetic  acid  and 
zinc  chloride,  benzaldehyde  and  acetyl  chloride  being  formed  ; 
the  necessary  amount  of  water  is  then  allowed  to  flow  in,  and 
the  acetic  acid  which  is  formed,  recovered.2 

The  benzaldehyde  thus  obtained,  which  always  contains 
chlorine  compounds,  is  used  in  the  colour  industry.  The  pure 
compound  may  be  obtained  from  it  by  preparing  the  double 
sulphite,  which  has  already  been  mentioned,  and  decomposing 
this  with  caustic  soda  solution. 

Properties. — Benzaldehyde  is  a  colourless,  strongly  refractive 
liquid  which  has  a  well  known  characteristic  smell  and  a  burn- 
ing aromatic  taste.  It  dissolves  in  more  than  300  parts  of  water ; 3 
boils  at  179°,  and  has  a  specific  gravity  of  T0636  at  0°  and  of 
1'0504  at  15°.  In  the  pure  state  it  rapidly  oxidizes  in  the  air  and 
is  also  oxidized  by  boiling  with  chromic  acid  solution,  manganese 
dioxide  and  sulphuric  acid,  or  freshly  precipitated  ferric  oxide.4 
It  is,  however,  only  slowly  attacked  by  strong,  boiling  nitric  acid  ; 
the  red,  fuming  acid  only  yields  benzoic  acid,  but  when  mixed 
with  sulphuric  'acid  gives  substitution  products.5  It  differs 
from  the  aldehydes  of  the  fatty  series  in  not  reducing  an  alkaline 
copper  solution.6 

1  Anschiitz,  Liebig's  Ann.  ccxxvi.  18. 

2  Ber.  Dcutsch.  Chem.  Ges.  xiii.  2013  ;  xiv.  1425. 

3  Fliickiger,  Jahresb.  Chem.  1875,  182. 

4  Grager,  Ann.  Chem.  Pharm.  cxi.  124. 

8  Lippmann  and  Hawliczek,  Ber.  Dcutsch.  Chem.  Ges.  ix.  1463. 
6  Tollens,  ibid.  xiv.  1950. 


BENZALDEHYDE.  135 


It  is  converted  into  benzyl  alcohol  by  treatment  with  sodium 
amalgam  and  water;  hydrobenzoin  is  simultaneously  formed, 
together  with  the  isomeric  isohydrobenzoin  C14H12(OH)2,  which 
compounds,  together  with  benzoin,  C6H5.CH(OH)CO.C6H5, 
obtained  by  heating  benzaldehyde  with  alcoholic  potassium 
cyanide  solution,  will  be  subsequently  described. 

Benzaldehyde  is  not  poisonous ;  when  taken  internally  it 
appears  in  the  urine  as  hippuric  acid ; l  it  is  not  decomposed 
when  heated  to  dull  redness,  but  is  decomposed,  chiefly  into 
benzene  and  carbon  monoxide,  when  passed  through  a  tube 
filled  with  pumice  stone  and  heated  to  bright  redness.2 

Benzaldehyde  readily  combines  with  other  carbon  compounds 
with  elimination  of  water  and  is  therefore  largely  employed, 
both  on  the  small  and  large  scale,  for  the  synthesis  of  con- 
densation products,  which  will  be  subsequently  described.  Only 
a  few  of  the  most  important  reactions  will  be  mentioned  here. 

(1.)  When  benzaldehyde  is  heated  with  sodium  acetate  and 
acetic  anhydride,  cinnamic  acid,  C6H5.CHz=OH.CO2H,  is  formed. 
The  homologues  of  this  acid  are  prepared  in  an  analogous 
manner  from  the  other  fatty  acids. 

(2.)  Aromatic  ke tones  are  easily  obtained  by  the  con-- 
densation  of  a  fatty  ketone  with  benzaldehyde;  thus  ordinary 
acetone  yields  methylcinnyl  ketone,  CH3.CO.CH=CH.C6H5, 
which  is  converted  by  the  further  action  of  benzaldehyde  into 
dicinnyl  ketone  or  cinnamone,  CO(CHz=CH.C6H5)2. 

(3.)  When  benzaldehyde  is  heated  with  aniline  and  zinc 
chloride,  diamidotriphenylmethane,  C6H5.CH(C6H4.NH2)2,  is 
obtained ;  if  dimethylaniline  be  employed,  the  base,  G6H5.CH 
(C6H4.N.(CH3)2)2,  is  formed,  and  this  yields  on  oxidation  the 
colouring  matter  known  as  benzaldehyde-green  or  malachite- 
green. 

(4.)  Benzaldehyde  combines  with  the  nitroparaffins  to  form 
aromatic  nitro-olefines,  such  as  phenylnitro-ethylene,  C6H,. 
CH=CHN02,  etc. 

1  Frerichs  and  Wohler,  Ann.  Chcm.  Pharm.Ixv.  337. 

2  Barreswill  and  BouJault,  ibid.  lii.  360. 


136  AROMATIC  COMPOUNDS. 


BENZIDENE  COMPOUNDS. 

2088  Benzaldehyde,  like  other  aldehydes,  behaves  as  the 
oxide  of  a  dyad  radical,  which  is  called  benzylene,  benzylidene 
or  benzidene.  As  in  all  analogous  cases,  the  corresponding 
alcohol  cannot  be  prepared,  but  ethers,  ethereal  salts,  and 
other  derivatives  are  known. 

Benzidene  diethyl  ether,  C6H5.CH(OC2H5)2,  was  obtained 
by  Wicke  by  the  action  of  benzidene  chloride  on  sodium 
othylate.  It  is  a  liquid  which  possesses  a  pleasant  smell 
resembling  that  of  the  geranium,  and  boils  at  222°.  Wicke 
has  also  prepared  various  other  ethers.1 

Benzidene  dichloride,  C6H5.CHC12.  Cahours  prepared  this 
compound  by  the  action  of  phosphorus  pentachloride  on  oil 
of  bitter  almonds 2  and  named  it  chlorobenzol,  a  name 
which  was  subsequently  changed  into  chloride  of  oil  of  bitter 
almonds  and  finally  into  benzal  chloride  (benzaldehyde  chloride), 
which  is  still  employed. 

It  is  also  obtained  by  treating  benzaldehyde  with  carbonyl 
chloride  or  succinyl  chloride  : 3 

xcci2X  xcox 

C6H5.CHO  +  G2H4<          >  =  C6H5.CHC12 + C.H/       )o. 
XX)  /  XCCK 

It  is,  however,  most  readily  prepared  by  passing  chlorine 
into  boiling  toluene  until  it  has  gained  75  per  cent,  in  weight 
and  then  purifying  the  product  by  fractional  distillation.4 

It  is  a  colourless  liquid  which  boils  at  206° — 207°  and 
has  a  specific  gravity  of  T295  at  16°. 5  In  the  cold  it  has  only 
a  feeble  smell,  but  when  heated  it  gives  off  a  penetrating 
vapour  which  produces  a  flow  of  tears.  It  is  manufactured 
and  employed  for  the  preparation  of  benzaldehyde. 

Benzidene,  dibromide,  C6H5.CHBr2,  is  formed  by  the  action  of 
phosphorus  pentabromide  on  benzaldehyde ;  it  is  a  powerfully 

1  Wicke,  Ann.  Chem.  Pharm.  cii.  363. 

2  Ann.  Chim.  Phys.  [3]  xxiii.  329. 

3  Rembold,  Ann.  Chem.  Pharm.  cxxxviii.  189. 

4  Beilstein  and  Kuhlberg,  ibid,  cxlvi.  322. 

5  Hiibner  and  Bente,  Ber.  Deutich.  Chem.  Ges.  vi.  804. 


BENZIDENE  COMPOUNDS.  137 

refractive  liquid,  which  can  only  be  distilled  without  decomposi- 
tion under  considerably  reduced  pressure.1 

Bcnzidcne  di-iodide,  C6H5.CHI2.     Geuther  and  Cartmell,  by 
the  action  of  hydriodic  acid  gas  on  benzaldehyde,  obtained  a 
peculiar  compound,  which  they  named  benzaldehyde  oxy iodide, 
C21H18I40 ;  it  forms  colourless,  rhombic  tablets,  which  melt  at 
28°  and  rapidly  become  coloured  dark  in  the  light.     It  smells 
exactly  like  cress,  and  can  be  volatilized  with  steam,  yielding 
a  vapour  which  attacks  the  eyes  and  nose  most  violently,  the 
dn  caused  being  greater  and  more  enduring  than  that  pro- 
luced  by  acrolein.    When  it  is  heated  with  silver  nitrate  solution, 
smell  of  benzaldehyde  is  produced.2 

The  constitution  of  this  body,  the   formula  of  which  can  be 
[pressed  as  C6H5.CHO  +  2C6H5.CHI2,  is  unknown. 
Benzidene  diacetate,  C6H5.CH(C2H302)2.     Wicke  obtained  this 
nnpound  by  the  action  of  silver  acetate  on  benzidene  chloride ; 3 
is   also   formed   when   benzaldehyde   is   heated   with   acetic 
ihydride,4   and  crystallizes   from   ether   in   small,   monoclinic 
iblets  or  in  twins,  which  have  the  swallow-tail  form  of  crystals 
)f  gypsum.     It  melts  at  45°— 46°,5  and  boils  at  2200.6 
Wicke    has    also    prepared    some    other   ethereal    salts    of 
mzidene. 

Potassium  benzidene  sulphite,  C6H5.CH(OH)S03K.  This 
)mpouiid,  which  was  earlier  called  the  bisulphite  of  benz- 
ildehyde-potash,  was  obtained  by  Bertagnini  in  crystals  by 
^itating  benzaldehyde  with  a  concentrated  solution  of  acid 
)tassium  sulphite.7  It  crystallizes  from  hot,  dilute  alcohol  in 
mg  plates,  which  are  slightly  soluble  in  cold  alcohol,  readily  in 
rater,  but  are  almost  insoluble  in  a  concentrated  solution  of  acid 
)tassium  .sulphite.  It  is  decomposed  by  simply  boiling  with 
iter,  more  readily  by  acids  or  alkalis,  with  separation  of  benz- 
ildehyde,  which  can  thus  be  obtained  pure  (p.  134). 
Sodium  benzidene  sulphite,  C6H5.CH(OH)SO3Na  +  H2O,  forms 
tall  crystals,  and  behaves  like  the  potassium  salt. 
Ammonium  benzidene  sulphite,  C6H5.CH(OH)S03NH4  +  H2O. 
irtagnini,  on  shaking  benzaldehyde  with  a  concentrated  solu- 
tion of  acid  ammonium  sulphite,  observed  an  evolution  of  heat 
id  obtained  a  clear  solution  from  which  no  crystals  separated  out. 

1  Michaelson  and  Lippmann,  Ber.  Dcutsch.  Chem.  Ges.    Suppl.  iv.  113. 

2  Ann.  Chem.  Pharm.  cxii.  20.  3  Ibid.  cii.  368. 
4  Geuther,  ibid.  cvi.  251  ;  Hiibner,  Zcitschr.  Chem.  1867,  277. 

s  Perkin,  ibid.  1868,  172. 

6  Neuhof,  Ann.  Chem.  Pharm.  cxlvi.  323.  1  Ibid.  Ixxxv.  183. 


138  AROMATIC  COMPOUNDS. 

Otto,  however,  obtained  the  compound  in  crystals  by  mixing 
alcoholic  solutions  of  sulphur  dioxide  and  hydrobenzamide  ;  a 
precipitate  is  formed  consisting  of  microscopic  needles  which  are 
slightly  soluble  in  alcohol,  readily  in  water,  and  separate  from 
the  latter  in  transparent  crystals  containing  three  molecules  of 
water.1 

Benzaldehyde  does  not  form  an  analogous  compound  with 
acid  aniline  sulphite,  but  a  very  stable  substance  of  the 
empirical  formula,  2C7H6O  +  2C6H7N  +  S02,  is  produced,  and 
crystallizes  from  water  in  long,  flat  needles.2 

Benzidene  sulphide,  C0H5.CHS.  Cahours  prepared  this  com- 
pound by  heating  benzidene  chloride  with  an  alcoholic  solution 
of  potassium  hydrosulphide  and  named  it  sulphobenzene.3  It 
was  then  further  investigated  by  Fleischer 4  and  Bottinger.5  It 
crystallizes  from  hot  alcohol  in  nacreous  plates  and  from  ether  in 
transparent,  four-sided  prisms,  melting  at  70° — 71°.  On  heating 
with  caustic  potash  it  yields  benzyl  hydrosulphide,  benzyl 
disulphide  and  some  benzoic  acid,  and  on  dry  distillation 
gives  stilbene,  C14H12,  tolallyl  sulphide,  CUH10S,  arid  thionessal, 

C23H20S- 

Pardbenzidene  sulphide,  (C6H5.CHS)n.  By  the  action  of  am- 
monium sulphide  on  an  alcoholic  solution  of  benzaldehyde, 
Laurent  obtained  a  compound  of  this  composition,  which  he 
called  sulphobenzoyl  hydride  (hydrure  de  sulfobenzo'ile),  and  de- 
scribed as  a  powder  consisting  of  microscopic  granules,  which 
became  soft  at  90° — 95°,  and,  after  careful  fusion,  solidified  to 
a  transparent  mass.  It  is  odourless,  but  imparts  to  the  hands  a 
very  repulsive,  adhering  alliaceous  odour.6  On  dry  distillation  it 
yields  the  same  products  as  benzidene  sulphide. 

The  compound  which  Klinger  obtained  by  passing  sulphuretted 
hydrogen  into  a  solution  of  benzaldehyde  in  absolute  alcohol  and 
named  a-benzothio-aldehyde,  is  probably  identical  with  this  body. 
It  is  amorphous,  softens  at  80° — 85°,  and  is  converted  by  acid 
chlorides  into  P~~benzothio-aldehyde,  which  is  slightly  soluble  in 
alcohol,  readily  in  hot  glacial  acetic  acid,  and  crystallizes  in 
lustrous  white  needles,  melting  at  225° — 2260.7 

This   compound    is    most    readily    obtained   by    dissolving 

1  Neuhof,  Ann.  Chem.  Pharm.  cxii.  308. 

2  Schiff,  ibid.  cxl.  130  ;  ccx.  128. 

3  Ann.  Chim.  Phys.  [3]  xxiii.  333  ;  Ann.  Chem.  Pharm.  Ixx.  40. 

4  Ibid.  cxl.  234.  5  Ber.  Deutsch.  Chem.  Gcs.  xii.  1053. 

6  Ann.  Chim.  Phys.  [3]  i.  292  ;  Ann.  Chem.  Pharm.  xxxviii.  320  ;  see  also 
Roehleder,  ibid,  xxxvii.  346.  7  Ber.  Deutsch.  Chem.  Ges.  ix.  1893. 


BENZALDOXIME.  139 


amorphous  benzothio-aldehyde  in  hot  benzene  and  adding  a  small 
quantity  of  iodine  also  dissolved  in  benzene  ;  lustrous  needles  of 
the  formula  C6H5.CHS  +  C6H6  soon  separate  out,  which  lose 
benzene  and  become  opaque  at  125° — 1300.1 

a-Benzothio-aldehyde  is  also  formed,  together  with  ammonia, 
when  an  alkaline  solution  of  benzothiamide,  C6H5.CS.NH2,  is 
treated  with  sodium  amalgam.2 

Both  thio-aldehydes,  when  heated  with  copper  dust,  yield 
stilbene,  C14H10,  as  the  chief  product,  and  the  amorphous  com- 
pound on  fusion  with  caustic  potash  yields  the  same  products  as 
benzidene  sulphide  (Bottinger).  Klinger  was  unable  to  convert 
the  latter,  which  he  considered  to  be  y-lenzotJiio-aldehyde,  into 
the  /3-compound  by  the  action  of  acetyl  chloride  or  iodine  ;  the 
^-compound  is  probably  a  polymeric  modification,  and  is  best 
called  parabenzidene  sulphide. 

2089  Benzidenoxime,  or  Benzaldoxime,  C6H5.CH.NOH,  is  formed 
when  benzaldehyde  and  sufficient  alcohol  to  form  a  clear 
solution  are  added  to  an  aqueous  solution  of  hydroxylamine 
hydrochloride  containing  an  excess  of  sodium  carbonate  : 

C6H5.CHO  +  H2N.OH  =  C6H5.CH=N.OH  +  H.2O. 

After  twenty-four  hours  the  mixture  is  extracted  with  ether 
id  the  residue,  after  the  evaporation  of  the  ether,  rectified. 
Benzaldoxime  is  an  oily  liquid,  which  boils  above  220°  with 
:ial  decomposition,  and  is  decomposed  by  hydrochloric  acid 
ito  the  substances  from  which  it  is  formed.  On  treatment  with 
)holic  caustic  soda  it  gives  the  compound  C6H5.CH.NONa, 
which  crystallizes  from  water  in  small,  lustrous  plates.  By  the 
action  of  methyl  iodide  on  this,  the  methyl  ether,  C6H5.CH, 
NOCH3,  is  obtained  as  a  light,  oily  liquid,  which  has  a  very 
pleasant,  fruity  odour,  and  boils  at  190° — 192°;  other  ethers  have 
been  prepared  in  a  similar  manner.3 

Hydrobcnzamide,  or  Tribenzidenediamine,  N2(CH.C6H6)8.  Acet- 
aldehyde  combines  directly  with  ammonia  to  form  aldehyde 
ammonia,  CH3.CH(OH)NH2,  but  benzaldehyde  behaves  in  a 
completely  different  manner ;  three  molecules  of  the  latter  lose 
all  their  oxygen,  which  combines  with  the  hydrogen  of  two 
molecules  of  ammonia,  the  place  of  this  being  taken  by  the 
benzidene  groups. 

1  Ber.  Deutsch.  Chem.  Ges.  x.  1877. 

2  Berathsen,  ibid,  x .  36. 

3  Petraczek,  ibid.  xv.  2783  ;  xvi.  823. 


140  AROMATIC  COMPOUNDS. 

Hydrobenzamide  is  slowly  formed  when  benzaldehyde  is 
allowed  to  stand  in  contact  with  aqueous  ammonia ; l  more 
rapidly  when  the  two  are  heated  together.2 

Benzaldehyde  absorbs  dry  ammonia,  and  if  the  product  of  this 
absorption  be  allowed  to  stand  in  a  vacuum,  water  is  lost  and 
hydrobenzamide  remains  ; 3  it  is  also  formed  when  benzidene- 
dichloride  is  allowed  to  stand  for  some  months  with  aqueous 
ammonia.4 

It  is  readily  soluble  in  alcohol  and  ether,  and  crystallizes  in 
lustrous,  rhombic  pyramids,  melting  at  110°;  very  fine  crystals 
may  be  obtained  by  pouring  an  excess  of  aqueous  ammonia  on 
to  a  mixture  of  equal  volumes  of  benzaldehyde  and  ether,  and 
allowing  the  whole  to  stand.5  It  is  tasteless,  but  its  alcoholic 
solution  has,  according  to  Laurent,  a  faint  taste  of  burnt 
almonds.  On  boiling  with  alcohol  it  slowly  decomposes  into 
ammonia  and  benzaldehyde  ;  acids  rapidly  produce  this  decom- 
position. On  oxidation  with  aqueous  chromic  acid,  a  large 
quantity  of  benzoic  acid  is  formed  (Fownes). 

When  it  is  boiled  with  caustic  potash  or  heated  to  120° — 130°, 
it  is  converted  into  the  isomeric  amarine,  which  will  be  sub- 
sequently described ;  the  relation  between  the  two  compounds 
is  shown  by  the  following  formulae  : 

Hydrobenzamide.  Amarine. 

C6H5.CH=NX  C6H5.C.NH 

>CH.C6H5.  |     >CN.C6H5. 

C6H5.CH=N/  C6H5.C.NH 

Thiobenzaldine,  (06H5.CH)3S2NH.  Laurent  obtained  this 
compound,  the  analogue  of  thialdine  (Pt.  II.  p.  75),  by  allowing 
a  mixture  of  crude  oil  of  bitter  almonds,  ammonium  sulphide 
and  ether,  to  stand  for  several  weeks.  It  crystallizes  in  nacreous 
plates  or  monoclinic  prisms  which  melt  at  125°,  and  impart 
an  unpleasant  smell  to  the  skin.  When  it  is  boiled  with 
alcohol,  sulphuretted  hydrogen  is  given  off,  while  alcoholic 
potash  decomposes  it  with  evolution  of  ammonia.6 

Benzidcne-aniline,  C6H5.CH=:N.C6H5.  Gerhardt  and  Laurent 
obtained  this  compound  by  heating  benzaldehyde  with  aniline, 

1  Laurent  (1836),  Ann.  Chim.  Phys.  Ixii.  23  ;  Ixvi.  18  ;  Ann.  Chem.  Phann. 
xxi.  130.  2  Rochleder,  ibid.  xli.  89. 

3  Herzfeld,  Ber.  Dcutsch.  Chem.  Ges.  x.  1271. 

4  Engelhardt,  Ann.  Chcm.  Pharm.  ex.  77. 

5  Eckmann,  ibid.  cxii.  175.  9  Ann.  Chem.  Pharm.  xxxviii.  323. 


CONDENSATION  PRODUCTS  OF  BENZALDEHYDE.   141 

and  named  it  benzoylanilide.1  The  same  compound  is  formed, 
as  shown  by  Schiff,  when  benzaldehyde  is  heated  with  thio- 
carbanilide  : 2 

3CS(NHC6H5)2  +  6C6H5.CHO  = 

6C6H5.CH  —  N.  C6H5  +  CS2 + 2CO2  4-  H2S  +  2H2O. 

It  is  very  soluble  in  alcohol  and  ether,  separating  from  the 
latter  in  warty  crystals,  and  crystallizing  from  carbon  disulphide 
in  yellow  needles,  which  melt  at  42°,3  and  are  volatile  with  steam. 
It  does  not  combine  with  acids,  and  is  partially  decomposed  on 
heating  into  benzaldehyde  and  aniline. 

2090  Benzidene-aniline  cyanhydrate,  C6H5.CH^N.C6H5.CNH. 
Cech  obtained  this  compound  by  the  action  of  potassium  cyanide 
on  an  alcoholic  solution  of  benzaldehyde  and  aniline  or  aniline 
hydrochloride ;  it  is  also  formed  when  hydrocyanic  acid  is  passed 
into  fused  benzidene-aniline,  and  is  decomposed  into  its  com- 
ponents by  heat.  It  crystallizes  from  carbon  disulphide  in  silky 
needles,  which  melt  at  82°,  sublime  readily,  and  are  volatile  with 
steam. 

Benzidenephenylhydrazine,  C6H5.CH:=N.NH.C6H5,  is  formed 
by  a  violent  reaction  when  benzaldehyde  and  phenylhydrazine 
are  brought  together.  It  crystallizes  from  dilute  alcohol  in 
monoclinic  prisms,  which  melt  at  152*5°  and  can  be  volatilized 
without  decomposition. 

Benzidenediphenylhydrazine,  C6H5.CH  =  NC.(C6H5)2,  forms 
small  yellow  crystals,  melting  at  1220.4 

Phenylbenzaldehydine,  or  Benzidene-orthodiamidolenzene,  (C6H5. 
CH=N)206H4,  is  formed  when  a  dilute  aqueous  solution  of 
orthodiamidobenzene  hydrochloride  is  shaken  up  with  benz- 
aldehyde, the  hydrochloride  thus  obtained  being  purified  by 
re-crystallization,  and  the  base  precipitated  with  caustic  potash. 

Phenylbenzaldehydine  is  insoluble  in  water  and  crystallizes 
from  alcohol  in  six-sided  prisms,  melting  at  133° — 134°. 

Phenylbenzaldehydine  hydrochloride,  C20H16N2.HC1,  crystallizes 
in  colourless  prisms  which  are  only  slightly  soluble  in  water,  and 
lose  hydrochloric  acid  when  their  solution  is  boiled. 

When  the  base  is  heated  with  ethyl  iodide  to  100°— 120°,  the 
compound  C20H16N2.C2H5I  is  formed ;  it  crystallizes  from  hot 
water  in  colourless,  thick  prisms,  melting  at  211° — 2130.5 

1  Jahresb.  Chem.  1850,  488.  2  Ann.  Chem.  Pharm.  cxlviii.  336. 

3  Cech,  Bcr.  Deutsch.  Chem.  Gfes.  xi.  246. 

4  E.  Fischer,  Ann.  Chem.  Pharm.  cxc.  134,  179. 

5  Engelbrecht  and  Ladenburg,  Ber.  Deutsch.  Chem.  Ges.  xi.  1653, 


142  AROMATIC  COMPOUNDS. 

Benzideneparadiamidobenzene,  (C6H5.CHi=:N)2C6H4,  is  formed 
by  the  action  of  paradiamidobenzene  on  benzaldehyde ;  it 
crystallizes  from  alcohol  in  plates  which  have  a  silver  lustre,  and 
melt  at  140° ;  it  is  decomposed  by  acids  into  its  components, 
since  only  the  ortho-diamines  form  stable  basic  aldehydines l 
(Part  III.  p.  62). 

Benzidenedimethylparadiamid.obenzene,  CCH5.CH  —  N.C6H4.N 
(CH3)2,  is  readily  formed  by  heating  benzaldehyde  with  di- 
methylparadiamidobenzene,  and  crystallizes  from  hot  alcohol  in 
lustrous  plates  or  needles,  melting  at  93°.  It  is  a  feeble,  di-acid 
base.2 

Dibenzidene-orthodiamidotoluene,  or  Tohibenzaldehydine,  (C6H5. 
CH=N)2C6H3.CH3,  has  been  obtained  by  Ladenburg  from 
orthodiamidotoluene ;  it  crystallizes  in  lustrous,  monoclinic 
prisms,  melting  at  195 '5° ;  on  oxidation  with  potassium  perman- 
ganate, it  yields  dibenzidenediamidobenzoic  acid,  (C6H5.CHi=:N)2. 
C6H3CO2H.  The  hydrochloride,  C21H18N2.C1H,  crystallizes  from 
hot  dilute  hydrochloric  acid  in  long  needles. 

When  it  is  heated  with  ethyl  iodide,  it  is  converted  into  the 
iodide,  C21H18N2.C2H5I,  which  crystallizes  in  thick  prisms,  and,  on 
treatment  with  silver  oxide,  yields  the  corresponding  hydroxide, 
which  remains  behind  after  evaporation  of  the  solution  as  a 
strongly  alkaline,  oily  liquid.3 

Dibenzidenemetadiamidotoluene  crystallizes  from  a  mixture  of 
ether  and  alcohol  in  small  lustrous  tablets,  melting  at  122° — 128°. 
It  does  not  combine  with  acids,  but  when  heated  to  140° — 150° 
for  a  considerable  time,  it  is  converted  into  a  base,  which  Schiff 
considers  to  be  amarine.4 

Benzidenephenyldiamine,  C6H5.CH(NH2)NH(C6H5).  When 
benzonitril,  C6H5.CN,  is  heated  with  aniline  hydrochloride  to 
220° — 240°,  phenylbenzenylamidine  5  is  formed,  and  this  is  con- 
verted into  the  diamine  by  the  action  of  zinc  and  dilute  acetic 
acid  : 

NH  XNH2 

C6H5.C^  +2H  =  C6H5.CH( 

\NH.C6H5  XNH.C6H5. 

It  is  very  soluble  in  all  solvents,  with  the  exception  of  water 
and  separates  from  dilute  alcohol  in  indistinct  crystals,  melting  at 

Ladenburg,  Ber.  Deutsch.  CJiem.  Ges.  xi.  599. 
Calm,  ibid.  xvii.  2938. 
Ibid.  x.  1126  ;  xi.  591,  1648. 
Ann.  Chcm.  Pharm.  cxl.  98. 
Bernthsen,  Liebig's  Ann.  clxxxiv.  348. 


BENZIDENE  UREIDES. 


143 


114"5° — 115°.  At  a  higher  temperature  it  distils  without  decom- 
position, and  on  heating  with  chloroform  and  alcoholic  potash 
yields  the  smell  of  the  carbamines. 

Benzidenephenylamine  hydrochloride,  C13H14N2.C1H,  crystallizes 
from  water  in  thick  prisms,  melting  at  223° — 224'5°.1 

Benzidene-acetamide,  C6H5.CH(NH.C2H30)2,  is  formed  by 
heating  benzaldehyde  with  acetamide,  and  crystallizes  from  hot 
water  in  fine  silky  needles.2 

Benzidene  urethane,  C6H5.CH(NH.CO.OC2H5)2,  is  formed  when 
hydrochloric  acid  is  added  to  a  mixture  of  benzaldehyde  and 
ethyl  carbamate.  It  separates  from  alcohol  as  a  silky  crystalline 
mass,  which  melts  at  171°,  and  can  be  sublimed.3 

Benzidene  ure'ides  are  formed  by  heating  benzaldehyde  with 
urea,  and  are  split  up  again  into  these  substances  by  boiling 
with  water.4 

,NH.CO.NH2 

Benzidenedi-ure'ide,     C6H,.CH\  ,  fine  needles. 


>enzidenetri-ureide, 


C6H5.CH< 


C6H5.CH 


,NH.CO.NH2 
>N— CO.NH2' 


,  white  powder. 


NH.CO.NH2. 
NH.CO.NH 


C6H5.CH<; 

\N—  CO.NH2 

mzidenetetra-ureide,  C6H5.CH<^  ,  white  powder. 

N_CO.NH2 


^TH.CO.NH2. 


lUBSTITUTION   PRODUCTS  OF  BENZIDENE 
COMPOUNDS. 

2091  Orthochlordbenzaldehyde,  C6H4C1.CHO.  By  the  action  of 
phosphorus  pentachloride  on  salicylaldehyde,  C6H4(OH)CHO, 
orthochlorobenzidene  chloride,  C6H4G1.CHC12,  is  obtained  as  an 

1  Bernthsen  and  Soymanski,  Ber.  Deutsch.  Chem.  Gcs.  xiii.  917. 

2  Roth,  Ann.  Chem.  Pharm.  cliv.  72. 

3  Bisclioff,  Ber.  Deutsch.  Chem.  Ges.  vii.  634,  1082. 

4  Schiff,  Ann.  Chem.  Pharm.  cxl.  115  ;  cxlviii.  330  ;  cli.  892. 


144  AROMATIC  COMPOUNDS. 

oily  liquid,  which  boils  at  227° — 230°,  and  possesses  a  penetrating 
smell  and  a  sharp  burning  taste.  When  this  compound  is  heated 
with  water  to  170°,  the  aldehyde  is  formed  ;  it  is  a  liquid  which 
boils  at  210°,  has  a  sharp  smell  and  taste,  and  readily  oxidizes  in 
the  air  to  orthochlorobenzoic  acid.  It  combines  with  acid  sodium 
sulphite.1 

Metachlorolwnzaldeliyde  is  formed  when  benzaldehyde  is 
chlorinated  in  presence  of  a  dehydrating  agent,  such  as  sul- 
phuric acid,  zinc  chloride,  aluminium  chloride,  etc.,  and  is  a 
liquid  boiling  at  210°— 2130.2 

It  may  also  be  obtained  by  heating  a  hydrochloric  acid 
solution  of  metamidobenzaldehyde  and  cuprous  chloride  to  the 
boiling-point  and  then  gradually  adding  a  solution  of  sodium 
nitrite.3 

Parachlorobenzaldeliydc  is  obtained  by  boiling  parachlorobenzyl 
bromide  with  water  and  lead  nitrate  in  an  atmosphere  of  carbon 
dioxide.  It  crystallizes  in  white  tablets,  melting  at  47'5°,  which 
are  slightly  soluble  in  cold,  more  readily  in  hot  water,  and  readily 
in  alcohol  ;  it  smells  like  benzaldehyde,  readily  oxidizes  in  the 
air  and  unites  with  acid  sodium  sulphite  to  form  a  compound 
which  is  only  slightly  soluble.4 

The  product  of  the  action  of  chlorine  on  benzidene  chloride 
in  presence  of  iodine  is  a  mixture  of  ortho-  and  para-chloro- 
benzidene  chlorides,  which  boils  at  230° — 2370,5  and  was  formerly 
thought  to  be  the  pure  para-compound.6  When  it  is  heated 
with  anhydrous  oxalic  acid,  boiled  with  lead  nitrate,  or  heated 
to  170°  with  water,  a  mixture  of  the  aldehydes  is  obtained, 
boiling  at  210° — 214° ;  in  the  cold  it  smells  like  benzaldehyde, 
but  when  heated  has  a  very  sharp,  penetrating  odour  arid  causes 
a  flow  of  tears.  The  same  mixture  is  formed,  together  with  ethyl 
iodide,  when  benzyl  ethyl  ether  is  treated  with  chlorine  in 
presence  of  iodine  : 7 

C6H5.CH2.O.C2H5  +  IC13:=C6H4C1.CHO  +  C2H5I  +  2HC1. 

DicUorolenzaldchyde,  C6H3C1,.CHO(C1 :  Cl  =  3  :  4).  Beilstein 
and  Kuhlberg,  by  the  action  of  chlorine  on  boiling  dichloro- 

Henry,  Bcr.  Dculsch.  Chcm.  Gc.s.  ii.  135. 

Miiller,  ibid,  xviii.  Ref.  viii.  660. 

Jbid.  xviii.  Ref.  '695. 

Jackson  and  White,  ibid.  xi.  1042. 

Anschiitz,  Ann.  Chcm.  Pharm.  ccxxvi.  19. 

6  Beilstein  and  Kuhlberg,  ibid,  cxlvi.  327. 

7  Sintenis,  Ber.  Deutsch.  Chcm.  Ges.  iv.  699. 


CHLORINE  DERIVATIONS  OF  BENZALDEHYDE.         145 

toluene,  obtained  a  dichlorobenzidene  chloride,  C6H3C1.2.CHC1.2,1 
which  boils  at  257°,  and  is  converted  into  the  aldehyde  by 
heating  with  water  to  200°.  It  is  soluble  in  boiling  water,  more 
readily  in  alcohol,  and  crystallizes  in  fine  needles,  which  melt  at 
68°,  volatilize  in  steam,  and  combine  with  acid  sodium  sulphite.2 
A  compound,  which  is  probably  identical  with  this,  is  ob- 
tained by  the  further  chlorination  of  metachlorobenzaldehyde 
in  presence  of  a  dehydrating  agent,  and  is  described  as  a  liquid, 
iling  at  240°— 2430.3 

a-Trichlorolenzaldehyde,  C6H2C13.CHO.      The  further  chlori- 
ion  of  a-trichlorotoluene  yields  a-trichlorobenzidene  chloride, 
jCl3.CHCl2,  which  boils  at   280°— 281°,  and  solidifies   be-' 
>w  0°  in  fine  needles.4     The  aldehyde  obtained  by  heating  it 
with  water  to  260°  is  insoluble  in  water,  crystallizes  in  very 
fine   needles,  which   melt   at    112° — 113°,  and  is  volatile  with 
steam.5 

ft-Trichlorobenzaldehyde.      The    /3-trichlorobenzidene    chloride 
ined  from  /3-trichlorotoluene,  melts  at  84°,  boils  at  280°,  and 
Ids  the  /3-trichlorobenzaldehyde  which  melts  at  90°  (Seelig). 
Tetrachlorobenzidene  chloride,  C6HC14.CHC12,  has  been  prepared 
>m  tetrachlorotoluene  ;  it  is  a  liquid,  which  boils  at  305° — 306°, 
and  is  decomposed  by  water  at  250°.    The  aldehyde  thus  formed 

not  been  further  investigated.6 

Pentachlorobenzidene  chloride,  C6C15.CHC12,  is  formed  by  the 
ntinued  action  of  chlorine  on  benzidene  chloride  in  presence 
iodine  and  finally  of  antimony  chloride.     It  crystallizes  from 
ohol  in  long  flat  plates,  melts  at  109°,  boils  at  334°,  and  is  not 
ttacked  'by  water  even  at  3000.7 

Orthobromobenzaldehyde,  C6H4Br.CHO,  has  been  prepared  by 
boiling  orthobromobenzyl  bromide  with  water  and  lead  nitrate  ; 
it  is  a  heavy,  oily  liquid,  which  oxidizes  very  rapidly  in  the  air.8 
Mctabromobenzaldehyde,  C6H4Br.CHO,  is  a  liquid  which  does 
not  solidify  in  a  freezing  mixture  (Jackson  and  White),  boils 
at  233° — 236°,  and  may  be  prepared  by  the  bromination  of 
benzaldehyde  in  presence  of  a  dehydrating  agent  (Muller). 

Parabromobenzaldehyde,    C6H4Br.GHO,    crystallizes    in    long 
white  needles,  melting  at  57°. 


Ann.  Chem.  Pharm.  cl.  291.  2  Ibid.  clii.  228. 

Ber.  Dcutsch.  Chem.   Gcs.  Kef.  xviii.  25. 

Ann.  Chem.  Pharm.  cl.  299  ;  Seelig,  Ber.  Dcutsch.  Chem.  Ges.  xviii.  420. 

Ibid.  ;  Ann.  Chem.  Pharm.  clii.  238. 

Ibid.  cl.  303.  7  1Ud.  cl.  306. 

Jackson  and  White,  Amer.  Chem.  Journ.  iii.  32. 


146  AROMATIC  COMPOUNDS. 

Para-iodobenzaldehyde,  C6H4I.CHO,  also  forms  needles,  melting 
at  73°  (Jackson  and  White). 

2092  Orthonitrobenzaldehyde,  C6H4(N02)CHO,  is  formed  in 
small  quantity,  together  with  the  m eta-compound,  by  the  action 
of  a  mixture  of  nitric  and  sulphuric  acids  on  benzaldehyde.1  It 
may,  however,  be  more  readily  prepared  from  orthonitrocinnamic 
acid,  C6H4(NO2)CH=CH.C02H.  When  the  ethyl  ether  of  this 
acid  is  dissolved  in  concentrated  nitric  acid  and  treated  with  sodium 
nitrite,  the  temperature  of  the  mixture  not  being  allowed  to  rise 
more  than  a  few  degrees,  a  compound  is  formed  which  contains 
a  nitric  acid  residue  in  the  side  chain.  The  mixture  is  poured, 
after  having  stood  for  some  hours,  into  water,  and  the  oil  which 
separates  out  distilled  in  steam,  sodium  carbonate  being  added 
from  time  to  time ;  the  distillate  consists  of  water  and  pure 
orthonitrobenzaldehyde.2  It  can  be  still  more  conveniently 
prepared  by  oxidizing  orthonitrocinnamic  acid  with  potassium 
permanganate  in  alkaline  solution  (Friedlander  and  Henriques). 
The  solution  must  be  cooled  with  ice  and  shaken  up  with 
benzene  at  short  intervals  in  order  to  remove  the  aldehyde  from 
the  further  action  of  the  oxidizing  agent.  The  benzene  solution 
is  then  evaporated,  the  aldehyde  remaining  behind.3 

It  is  readily  soluble  in  alcohol,  slightly  in  water,  and  crystal- 
lizes in  long,  light  yellow  needles,  melting  at  46°,  which  smell 
like  benzaldehyde  in  the  cold,  but  give  off  a  penetrating  vapour 
when  heated. 

It  forms  a  readily  soluble  compound  with  acid  sodium  sulphite, 
which  crystallizes  in  small,  lustrous  plates  ;  concentrated  caustic 
soda  solution  decomposes  it  completely  into  orthonitrobenzyl 
alcohol  and  orthonitrobenzoic  acid.  When  a  little  water  and 
caustic  soda  are  added  to  its  solution  in  acetone,  indigotin, 
C16H10N2O2,  the  colouring  matter  of  indigo,  separates  out  after 
a  short  time.4 

Orthonitrobenzaldoxime,  C6H4(NO2)CH.NOH.  Gabriel  and 
Meyer,  by  the  action  of  hydrochloric  acid  and  amyl  nitrite  on 
amidorthonitrophenylacetic  acid,  obtained  a  diazo-compound  : 

NH2.C6H3(N02)CH2.C02H  +  2NO2H  +  HC1  = 

C1N  =  NC6H3(NO2)CH2NO  +  CO2+ 3H2O. 

1  Rudolph,  Ser.  De,utsch.  Chem.  Gcs.  xiii.  310.     . 

2  Friedlander  and  Henriques,  ibid.  xiv.  2801. 

3  Einhorn,  ibid.  xvii.  119. 

4  Baeyer  and  Drewsen,  ibid.  xv.  2857. 


METANITROBENZ  ALDEHYDE. 


147 


On  heating  with  alcohol,  this  is  converted  into  nitroso- 
methylnitrolenzene,  C6H4(NO2)CH2NO,  this  being  decomposed  by 
oxidation  with  formation  of  nitrogen  monoxide  and  orthonitro- 
benzaldehyde,  which  was  first  prepared  pure  by  this  method.1 

This  substance  was  subsequently  recognised  as  orthonitrobenzal- 
doxime  and  prepared  from  the  aldehyde  and  hydroxylamine.2 
crystallizes  from  hot  water  in  hair-like  needles,  which  melt 
95°,  have  a  sweet  taste,  and  form  a  yellow  solution  in  alkalis, 
methyl  ether,  C^H/NCgCH.NOCHg,  is  formed  by  heating 
to  100°  with  caustic  potash,  methyl  alcohol  and  methyl  iodide  ; 
is   only   slightly  soluble   in   water,   readily   in  alcohol,   and 
stallizes  in  silky  needles,  melting  at  58°. 

Metanitrobcnzaldehyde,  C6H4(NO2)CHO,  was  first  obtained  by 
jrtagnini  by  the  action  of  a  mixture  of  nitric  and  sulphuric 
;ids  on  benzaldehyde.3  In  order  to  prepare  it,  1  part  of  the 
ir  is  dissolved  in  a  mixture  of  5  volumes  of  fuming  nitric 
with  10  volumes  of  sulphuric  acid,  the  temperature  being 
:ept  below  15°.  The  nitro-compound  is  precipitated  by  water, 
shed  and  re-crystallized  from  dilute  alcohol.4  It  forms  lustrous 
rhite  needles,  melting  at  58°,  5  smells  like  benzaldehyde  when 
)ld,  but  gives  off  a  penetrating  vapour  when  heated,  and 
combines  with  the  acid  sulphites  of  the  alkalis  (Bertagnini),  as 
fell  as  with  acid  aniline  sulphite  6  to  form  crystalline  compounds. 
Metanitrobenzidene  chloride,  C6H4(NO2)CHC12,  is  obtained  by 
action  of  phosphorus  pentachloride  on  the  aldehyde ;  it 
stallizes  from  alcohol  in  needles  or  small  thin  plates,  melting 
65°.7 

Metanitrobenzidene  bromide,  C6H4(NO2)CHBr9,  is  formed  by 
heating  the  aldehyde  with  bromine  to  140°,  and  crystallizes  in 
microscopic  tablets,  melting  at  101° — 1020.8 

Metanitrobenzaldoxime,  CgH/NO^CH.NOH,  was  first  obtained 
from  metanitro-amidophenylacetic  acid  and  was  called  nitroso- 
methylmetanitrobenzene? 

It  is  readily  formed  by  the  combination  of  hydroxylamine 


1  Ber.  Deutsch.  Chem.  Ges.  xiv.  832,  2332. 

2  Gabriel,  ibid.  xv.  3057. 

3  Ann.  Chem.  Pharm.  Ixxix.  260. 

4  Widmann,  Ber.  Deutech.   Chem.   Ges.   xili.  678 
Henriques,  ibid.  xiv.  2801. 

5  Lippmann  and  Hawliczek,  ibid.  ix.  1463. 
8  Sctnff,  Ann.  Chem.  Pharm.  cxcv.  301. 

7  Widmann,  Ber.  Deutsch.  Chem.  Ges.  xiii.  676. 

8  Wachendorff,  Ann.  Chem.  Pharm.  clxxxv.  266. 

9  Gabriel,  Ber.  Deutsch.  Chem.  Ges.  xv.  834. 


see   also   Friedlander  and 


148  AROMATIC  COMPOUNDS. 

with  metanitrobenzaldehyde,1  and  crystallizes  from  water  in  long, 
flat  needles,  melting  at  118° — 119°.  Its  methyl  ether  also  forms 
flat  needles  and  melts  at  63°— 63'5°. 

Trinitrohydrobenzamide,  N2(CH.C6H4.NO.2)3,  is  formed  by  the 
action  of  ammonia  on  metanitrobenzaldehyde ;  it  is  insoluble  in 
water  and  ether,  and  only  slightly  soluble  in  boiling  alcohol,  from 
which  it  separates  out  in  flocks  consisting  of  very  thin  needles. 
When  it  is  heated  to  125°  or  boiled  with  dilute  caustic  potash 
solution,  it  is  converted  into  the  isomeric  trinitro-amarine,  which 
forms  warty  crystals  and  has  a  feeble  alkaline  reaction.  Its  salts 
are  difficultly  soluble  and  have  a  very  bitter  taste  (Bertagnini). 

Paranitrobenzaldehyde,  C6H4(N02)CHO,  is  prepared  by  boiling 
10  parts  of  paranitrobenzyl  chloride  with  60  parts  of  water,  14 
parts  of  lead  nitrate,  and  10  parts  of  nitric  acid  of  sp.  gr.  T3, 
for  several  hours.  If  the  solution  be  more  dilute,  nitrobenzyl 
alcohol  is  formed  instead  of  the  aldehyde.  The  product  is  shaken 
out  with  ether  and  the  aldehyde  separated  by  means  of  acid 
sodium  sulphite.2 

Paranitrobenzaldehyde  may  also  be  readily  obtained  by  the 
oxidation  of  paranitrocinnamic  acid.3  It  crystallizes  from  hot 
water  in  thin  prisms,  often  an  inch  in  length,  which  melt  at 
106°,  have  a  characteristic  smell,  and  do  not  volatilize  readily 
in  steam.  Its  compound  with  acid  sodium  sulphite  is  readily 
soluble  in  water  and  crystallizes  in  small  iridescent  plates. 
It  is  not  attacked  to  an  appreciable  extent  by  boiling  nitric 
acid,  which  must  not,  however,  be  too  concentrated,  but  is 
quantitatively  converted  into  parahydroxybenzoic  acid  by 
chromic  acid.4 

When  it  is  heated  with  aniline  hydrochloride  and  zinc 
chloride,  paranitrodiamidotriphenylmethane,  CH(C6H4.NH2)2 
C6H4.N02,  is  formed,  which  on  reduction  yields  paraleucaniline, 
CH(C6H4.NH2)3.  It  is  oxidized  by  mercuric  oxide  to  pararosani- 
line,  C(OH)(C6H4.NH2)3  (Fischer  and  Greiff). 

Paranitrobenzidene  chloride,  C6H4(NO2)CHC12;  is  formed  by 
the  action  of  phosphorus  pentachloride  on  paranitrobenzalde- 
hyde  ;  it  crystallizes  from  alcohol  in  short,  well-formed  prisms, 
melting  at  46°. 5 

Paranitrobenzidene  bromide,  C6H4(NO2)CHBr2,  is  formed  by 

1  Gabriel,  Ber.  Dcutscli.  Chem.  Gcs.  xv.  3061. 

2  O.  Fischer  and  Greiff,  ibid.  xiii.  669. 

8  Baeyer,  ibid.  xiv.  2317  ;  Friedlander,  ibid.  xiv.  2577  ;  Easier,  ibid.  xvi.  2714. 

4  0.  Fischer,  ibid.  xiv.  2525. 

5  Zimmermann  and  Miiller,  ibid,  xviii.  996. 


ORTHAMIDOBENZALDEHYDE.  149 


heating  paranitrotoluene  with  bromine  to  140°,  and  crystallizes 
from  alcohol  in  needles  or  small  rectangular  plates,  melting  at 
°—  82-50.1 

Both   compounds   are   converted    into    pararosaniline    when 
ted  with  aniline.2 

Paranitrdbenzaldoxime,  C6H4(N02)CH=iN.OH,  crystallizes 
m  hot  water  in  long  needles,  melting  at  128'5°.3 
2093  Orthamidobenzaldehyde,  C6H4(NH2)CHO,  was  first  ob- 
ined  by  Gabriel  in  small  quantities  by  oxidizing  orthamido- 
nzaldoxime  with  an  acid  solution  of  ferric  chloride.4  Fried- 
lander  and  Henriques  found  that  orthonitrobenzaldehyde  is 
converted  by  the  action  of  tin  and  acetic  acid  into  anthranil,5 
C7H5NO,  a  compound  which  stands  to  anthranilic  acid  or 
orthamidobenzoic  acid  in  the  same  relation  as  lactimide  to 
a-amidopropionic  acid  (Part  II.  p.  142).  This  is  converted 
into  orthamidobenzaldehyde  by  heating  with  ferrous  sulphate 
.d  ammonia  :  6 


C6H4      |      +  2H  =  06H 

\CO  CHO. 

The  latter  can  also  be  obtained  directly  in  the  same  way  from 
thonitrobenzaldehyde.7     It   is    very   soluble   in   alcohol,   less 
lily  in  water,  forming  a  yellow  solution,  and  crystallizes  in 
strous  plates,  which  are   volatile   with   steam,  their  vapour 
sessing  a  penetrating  smell  resembling  that  of  an  indigo  vat. 
[t  melts  at  39°  —  40°,  and  solidifies  on  cooling  in  a  crystalline 
lass;   at   a  higher  temperature  a  portion  distils  without  de- 
>mposition,   while    the  remainder  is   converted   into   a   dark 
jllow,  resinous  mass.      It  can  be  heated   with    caustic   soda 
)lution  or  ammonia  without  undergoing  any  change  ;   dilute 
tineral  acids,  however,  readily  convert   it  into  an  amorphous 
mdensation  product.     When  it  is  heated  with  acetic  anhydride, 
acdylorthamidolenzaldehyde,  C6H4(NH.C2H3O)CHO,  is  formed; 
it  crystallizes  from  hot  water  in  long  white  needles,  melting  at 
70°—  71°. 

Orthamidobenzaldoxime,  C6H4(NH2)CH=N.OH,  is  formed  by 

1  Wachendorft',  Ann.  Chem.  Pharm.  clxxxv.  268. 

2  Zimmermarm  and  Miiller,  Ber.  Deutsch.  'Chem.  Ges.  xvii.  2936. 

3  Gabriel  and  Herzberg,  ibid.  xvi.  2000. 

4  Ber.  Deutsch.  Chem.  Ges.  xv.  2004. 

5  Ibid.  xv.  2105. 

6  Friedlander,  ibid.  xv.  2572. 

7  Friedlander  and  Coining,  ibid.  xvii.  456. 

241 


150  AROMATIC  COMPOUNDS. 

the  reduction  of  the  corresponding  nitro-compound  with  am- 
monium sulphide,  and  crystallizes  from  hot  water  in  long,  flat, 
lustrous  needles,  melting  at  132° — 1330.1 

Metamidobenzaldeliyde,  C6H4(NH2)CHO,  is  obtained  hy  re- 
ducing metanitrobenzaldehyde  with  ammonia  and  ferrous 
sulphate,  and  distilling  the  product  with  steam ;  it  is  a  yellow, 
oily  liquid,  which  solidifies  at  low  temperatures  and  yields 
amorphous  condensation  products  with  even  greater  readiness 
than  the  ortho-compound  (Friedlander  and  Gohring). 

Metamidobenzaldoxime,  C6H4(NH2)CH:=N.OH,  is  formed 
when  a  solution  of  metanitrobenzaldoxime  in  caustic  soda  is 
added  to  a  hot  solution  of  ferrous  sulphate  saturated  with 
ammonia,  the  blue-black  ferrous  hydroxide  being  converted 
into  brown  ferric  hydroxide.  The  filtrate  is  rendered  faintly 
acid  with  hydrochloric  acid,  treated  with  ammonia  and  then 
extracted  with  ether;  the  residue  left  on  evaporation  of  the 
ethereal  extract  consists  of  metamidobenzaldoxime,  which 
crystallizes  from  hot  benzene  in  fine,  snow-white  needles,  melt- 
ing at  88°.  Oxidation  with  an  acid  solution  of  ferric  chloride 
yields  an  amorphous,  yellow  oxidation  product  of  metamido- 
benzaldehyde.2 

Paramidobenzaldehyde,  C6H4(NH2)CHO,  has  been  obtained  as 
a  decomposition  product  of  its  aldoxime  ;  it  crystallizes  from 
water  in  small,  indented  plates,  which  melt  at  69'5° — 71 '5°,  but 
soon  change  into  a  modification  insoluble  in  water  and  melting 
at  a  higher  temperature.  When  heated  with  acetic  anhydride 
and  sodium  acetate,  it  is  converted  into  acetylparamidobenzalde- 
hyde,  C6H4(NH.C2H3O)CHO,  which  crystallizes  from  hot  water 
in  long,  lustrous  needles,  melting  at  155°. 

Paramidobenzaldoxime,  C6H4(NH2)CHi=N.OH,  is  formed  by 
the  action  of  ammonium  sulphide  on  paranitrobenzaldoxime, 
and  crystallizes  from  hot  water  in  yellow  tablets,  melting  at 
124°.  It  dissolves  in  an  excess  of  hydrochloric  acid,  forming  a 
solution  which  soon  deposits  dark  red  needles  with  a  blue  re- 
flection, while  hydroxylamine  remains  in  solution.  Caustic  soda 
decomposes  the  red  compound,  paramidobenzaldehyde  or  its  con- 
densation products  being  set  free.3 

Dimethylparamidobenzaldehydc,  C6H4.N(CH3)2CHO.  When 
zinc  chloride  is  allowed  to  act  on  a  mixture  of  chloral  hydrate 

1  Gabriel  and  Mayer,  Ber.  Deutsch.  Chcm.  Ges.  xiv.  2338. 

2  Gabriel,  ibid.  xvi.  1997. 

3  Gabriel  and  Herzberg,  ibid.  xvi.  2000, 


BENZOIC  ACID.  151 


dimethylaniline,  dimethylamidophenylhydroxytrichlorethane 
is  formed,  and  is  decomposed  by  caustic  potash  with  formation  of 
lethylparamidobenzaldehyde  and  chloroform  or  decomposition 
iucts  of  these  : 

/CHO 
C6H/  +CHC13. 

\N(CH3)2  XN(CH3)2 

The  new  compound  crystallizes  in  small  plates,  which  melt  at 
73°,  readily  dissolve  in  alcohol  and  hot  water,  and  are  volatile 
with  steam.1 


BENZOIC  ACID,  C6H5.COOH. 

94  The  products  formed  by  the  dry  distillation  of  gum  ben- 
in  2  are  mentioned  in  writings  which  date  back  as  far  as  the 
sixteenth  century.  Hieronymus  Rosello,  who,  under  the  name 
of  Alexius  Pedemontanus,  published  a  work,  De  Secretis,  in  the 
year  1557,  mentions  in  it  the  butter  of  benzoin,  and  Libavius 
in  his  Alchymia,  written  in  1595,  says  that  when  laser*  vel 
in  is  distilled,  water  comes  over  first,  followed  by  a  thick 
.,  "  ultima  exit  instar  mannae,  gummi."  Blaise  de  Vigenere, 
whose  TraiU  de  feu  et  du  sel,  appeared  after  his  death  in  1608, 
ys  that  with  a  strong  fire  "  infinies  petitcs  aiguilles  et  fila- 
appear,  which  must  be  soon  removed  because  they 
would  otherwise  melt  like  marrow  (moelle).  About  the  same 
period,  Turquet  de  Mayerne  in  his  Pharmacopoea  teaches  how  to 
obtain  flowers  of  benzoin  from  the  residue  by  subliming  it  in  an 


says  1 
ments 

Tir/-\-n  1  r\ 


1  Rocssneck,  Ber.  Deutsch.  Chem.  Ges.  xviii.  1516  ;  xix.  365. 

2  This  resin  is  obtained  by  means  of  incisions  in  the  bark  of  Styrax  Benzoin,  a 
tree  indigenous  to  Java  and  Sumatra.     It  is  sent  into  the  European  market  from 
the  latter  island,  and  this  was  formerly  the  only  source  from  which  it  could  be 
obtained.     A  highly  valued  variety  is  now  sent  from  Siam,  but  nothing  further  is 
known  as  to  its  origin.     It  was  formerly  counted  as  one  of  the  costly  spices.     It 
is  first  mentioned  by  Ibn  Batuta,  who  travelled  in  the  East  about  the  years  1325 
— 1349,  and  describes  it  under  the  name  of  Luban  Javvi  (incense  of  Java).     The 
latter  word  was  then  the  name  of  Sumatra,  and  the    \rnbs  designated  by  it  the 
whole  archipelago,  as  well  as  the  products  obtained  from  it.     The  Arabic  name 
gradually  became  corrupted  into  banjawi,  benjui,  benzui,  benzoe,  benzoin,  and  in 
English  also  benjamin   or  gum  benjamin,    which  is  now  the  name    in  general 
commercial  use  (Fliickiger  and  Hanbury,  Pharmacographia,  2nd  ed.  p.  403). 

3  Laser  is  the  name  of   a  Persian  and  Indian  product  on  which  a  tax  was 
imposed  at  the  Roman  customs-house  in  Alexandria  during  the  second  century  of 
our  era.     Some  suppose  that  it  was  asa  foetida,  while  benzoe  was  also  called 
asa  dulcis. 


152  AROMATIC  COMPOUNDS. 

earthen  vessel  to  which  a  cap  of  paper  has  been  adapted,  or  by 
heating  it  mixed  with  sand  in  a  retort,  and  since  that  time 
flores  benzoes  have  been  an  ordinary  pharmaceutical  prepara- 
tion. A  solution  of  the  resin  in  alcohol  was  also  in  use ;  mixed 
with  lead  acetate  it  was  employed  as  a  choice  cosmetic  under 
the  names  of  magisterium  lenzoes  or  lac  virginis.  Ehrenfried 
Hagendorn,  a  physician  of  Gorlitz,  in  1671  found  in  this  a  salt 
which  was  identical  with  flowers  of  benzoin,  both  in  smell  and 
taste.  Lemery  in  1675  also  remarked  on  the  acid  nature  of 
this  substance,  saying,  "  les  fleurs  de  lenjoin  ont  une  addiU 
fort  agrdable"  a  fact  which  was  further  proved  by  the  researches 
of  Scheele,  who  showed,  in  1775,  that  the  flowers  of  benzoin  could 
be  more  economically  obtained  by  digesting  the  resin  with 
slaked  lime  and  water  for  some  hours,  boiling  and  adding 
hydrochloric  acid  to  the  filtrate;  finally,  Lichtenstein  in  1782 
conclusively  proved  that  they  are  an  acid. 

The  correct  composition  of  benzoic  acid  was  determined  in 
1832  by  Liebig  and  Wohler,1  who  showed  that  it  is  a  compound 
of  the  radical  benzoyl,  C7H6O  (p.  89).  Mitscherlich,  on  the 
other  hand,  showed  in  1834  that  it  is  decomposed  into  carbon 
dioxide  and  benzol  on  heating  with  milk  of  lime,  and  looked 
upon  it  as  a  carbonic  acid  derivative  of  benzol ;  Liebig  opposed 
this  view,  as  he  considered  the  benzol  to  be  merely  a  product  of 
the  destruction  of  the  benzoic  acid  ;  the  latter  compound  can, 
however,  as  was  shown  somewhat  later,  be  readily  prepared 
synthetically  from  carbon  dioxide  and  benzol,  and  we  can 
therefore  look  upon  it  as  carbonic  acid,  CO(OH)2,  in  which  one 
hydroxyl  has  been  replaced  by  phenyl,  or  as  a  compound  of 
phenyl  with  carboxyl.  The  latter  supposition  corresponds  to 
that  of  Berzelius,  according  to  which,  benzoic  acid  is  oxalic  acid 
copulated  with  phenyl,  oxalic  acid  being  dicarboxyl. 

Many  varieties  of  benzoin  contain  cinnamic  acid  2  in  addition 
to  benzoic  acid  and  frequently  only  the  former.3  Both  these 
acids  occur,  either  free  or  in  the  form  of  ethereal  salts,  together 
with  other  aromatic  compounds,  in  Tolu  balsam  (p.  1),  Peru 
balsam  (concerning  which  Lehmann  had  already  stated  in  his 
Dissertation  de  balsamo  peruviano  (1709),  that  on  decomposition 
it  yields  flowers  resembling  flowers  of  benzoin),  Mecca  balsam 
(Balsamodendron  Opobalsamum  et  gileadensis),  myrrh  (B.  Myrrlia), 

1  Ann.  Ohem.  Pharm.  iii.  249. 

2  Kolbe  and  Lautemann,  ibid.  cxix.  136  ;  Fliickiger,  Pharmacographia. 

3  Aschoff,  Jahrcsb.  1861,  400. 


OCCURRENCE  OF  BENZOIC  ACID.  153 

liquid  styrax,  acaroid  resin  (Xantlwrrheo  hastilis),  dragon's  blood 
and  other  resins.  Benzoic  acid  has  also  been  found  in  the  per- 
fume known  as  hilan-hilan  or  ilang-ilang,  which  is  prepared 
from  the  flowers  of  Unona  odoratissima}  as  well  as  in  plums 
(Prunus  domestica  clilorocarpaf  and  the  cranberry.3  It  also 
occurs  in  vanilla,  the  fruit  of  the  clove-tree,  the  seeds  of  the 
spindle-tree  (Eiwnymus  europaeus)  and  the  root  of  the  sweet 
flag  (Acorus  calamus),  &c.  The  coumarin  which  occurs  in 
Holcus  odoratus,  Anthoxanthum  odoratum  (sweet-scented  vernal 
grass),  and  woodruff  was  at  one  time  mistaken  for  benzoic 
acid. 

In  the  year  1776,  Rouelle  stated  that  the  urine  of  the  cow 
and  the  camel  contains  a  salt  similar  to  flowers  of  benzoin,  and 
Scheele,  in  1785,  obtained  a  substance,  the  properties  of  which 
agreed  with  those  of  benzoic  acid,  by  extracting  with  alcohol 
the  solid  residue  left  on  the  evaporation  of  urine  and  treating 
the  "  soapy  extract "  with  nitric  acid.  Fourcroy  and  Vauque- 
lin  found,  in  1797,  that  the  urine  of  gramimvora  contains 
benzoic  acid,  but  Liebig,  in  1829,  showed  that  this  substance  is 
a  new  nitrogenous  acid,  which  he  named  hippuric  acid,  and 
which  splits  up  when  the  urine  is  allowed  to  stand,  yielding 
benzoic  acid.  According  to  some  observers,  however,  benzoic 
acid  frequently  occurs  along  with  hippuric  acid  in  the  urine, 
and  it  has  also  been  found  in  a  gland  in  the  beaver,4  and  in  the 
kidneys  of  the  ox.5  It  is  probable  that  in  all  these  cases  the 
acid  is  formed  by  the  decomposition  of  hippuric  acid. 

It  has  also  been  observed  as  a  decomposition  product  of 
various  alkaloids,  such  as  atropine,  cotoine,  &c.,  and  is  formed 
in  small  quantity  by  the  oxidation  of  albuminoids.  It  may  be 
obtained  in  large  quantities  by  the  oxidation  of  those  aromatic 
compounds  which  possess  a  side  chain  containing  carbon 
(Part  III.  p.  12).  It  also  occurs  in  coal-tar.6 

The  various  synthetical  methods  by  which  it  has  been  pro- 
duced have  already  been  given  (Part  III.  p.  30). 

2095  It  was  formerly  prepared  exclusively  from  gum  benzoin, 
and  the  acid  used  in  medicine  is  still  obtained  from  it  by  sublima- 
tion ;•  it  always  contains  a  small  amount  of  an  ethereal  oil,  which 

1  Gal,  Ber.  Deutsch.  Chem.  Ges.  vi.  824. 

2  Ducheek,  Gmelin's  Org.  Chem.  v.  332. 

3  Loew,  Journ.  Prakt.  Chem.  [2]  xix.  312. 

4  Wohler,  Ann.  Chem.  Pharm.  Ixvii.  360. 

5  Seligsohn,  Chem.  Centralbl.  1861,  241. 

6  Schuke,  Ber.  Deutsch.  Chem.  Ges.  xviii.  615. 


154  AROMATIC  COMPOUNDS. 

gives  it  its  peculiar  smell.1  In  order  to  obtain  it  in  this  way, 
the  coarsely  powdered  resin  is  heated  to  about  170°  in  a  flat 
iron  vessel ;  this  is  covered  with  filter-paper  and  fitted  with  a 
conical  cap  of  strong  paper,  in  which  the  acid  collects.2  Accord- 
ing to  Wohler,  the  gum  benzoin  is  dissolved  in  an  equal  volume 
of  absolute  alcohol  and  fuming  hydrochloric  acid  added  to  the 
hot  solution  until  the  resin  commences  to  separate  out ;  it  is 
then  distilled,  water  being  added  at  intervals,  and  the  distillate, 
which  contains  ethyl  benzoate,  warmed  with  caustic  potash  and 
then  heated  to  boiling  and  saturated  with  hydrochloric  acid. 
Benzoic  acid  separates  out  on  cooling  and  is  found  to  possess 
precisely  the  same  smell  as  the  sublimed  acid.3 

In  order  to  extract  the  acid  from  the  resin  by  Scheele's 
method,  it  is  well  mixed  with  an  equal  weight  of  slaked  lime, 
repeatedly  boiled  out  with  water,  the  filtrate  evaporated  to 
one -sixth  of  its  original  bulk,  treated  with  bleaching-powder 
solution,  and  then  boiled  with  hydrochloric  acid  until  all  the 
chlorine  has  been  removed.  The  acid  separates  out  on  cooling 
and  is  re -crystallized  from  hot  water.4 

It  is  prepared  from  the  urine  of  cows  or  horses  by  allowing  it 
to  stand  for  several  days,  clarifying  with  milk  of  lime,  evaporating 
the  liquid  to  one-fourth  of  its  bulk  and  precipitating  the  benzoic 
acid  with  hydrochloric  acid.  Since  the  evaporation  produces 
a  very  unpleasant  smell,  it  is  better  to  precipitate  the  excess 
of  lime  by  carbonic  acid  and  add  ferric  chloride,  to  precipitate 
ferric  benzoate,  which  is  then  decomposed  by  hydrochloric  acid. 
The  acid  thus  obtained  is  purified  by  being  redissolved  in  milk 
of  lime  with  the  addition  of  a  little  bleaching-powder  solution, 
separated  by  hydrochloric  acid  and  re-crystallized  from  hot  water. 
The  final  product  (acidum  benzoicum  ex  urina)  still  smells  of 
urine,  and  is  not  employed  for  pharmaceutical  purposes.  The 
smell  may,  however,  be  disguised  by  the  addition  of  some  of  the 
sublimed  acid.  About  two  kilos,  of  acid  are  obtained  from 
1,000  kilos,  of  urine.5 

P.  and  E.  Depouilly  have  proposed  to  obtain 'benzoic  acid 
from  phthalic  acid,6  which  is  obtained  by  the  oxidation  of 

1  Jacobsen  found  in  it  methyl  benzoate,  benzyl  benzoate,  vanillin,   guiacol, 
catechol  and  other  aromatic  compounds  (Ber.  Deutsch.   Chcm.   Ges.   xvii.   Kef. 
354). 

2  Mohr,  Ann.   Chem.   Pharm.   xxix.  117  ;  Lowe,  Journ.  Prakt.  Chcm.  cviii. 
257. 

3  Ann.  Chem.  Pharm.  xlix.  245.  4  Stenhouse. 

5  Hofmann,  Ber.  Enlw.  Chem.  2nd.  ii.  431. 

6  Jahrcsb.  Chcm.  1865,  323. 


PREPARATION  OF  BENZOIC  ACID.  155 

naphthalene  and  is  now  manufactured  on  the  large  scale. 
When  its  calcium  salt  is  heated  to  330° — 350°  with  slaked  lime 
in  absence  of  air,  calcium  benzoate  and  calcium  carbonate  are 
)rmed  : 


2C6H4(C02)2Ca  +  Ca(OH)2  =  (C6H5.CO2)2Ca  +  2CO3Ca. 


. 

According  to  the  method  of  Laurent  and  Castelhaz,1  acid 
ammonium  phthalate  is  converted  into  phthalimide  by  heating, 
and  this  is  then  distilled  with  lime,  benzonitril  being  formed  : 

C=NH 

"  =  C6H5CN  +  CaC03  +  H2O. 


; 


The  benzonitril  is  then  converted  into  benzoic  acid  by  boiling 

with  caustic  soda  solution. 

Benzoic  acid  is  now  generally  prepared  from  toluene  ;  this  may 
simply  oxidized  by  boiling  with  dilute  nitric  acid,  but  it  is 
ore  advantageous  to  first  convert  it  into  benzyl  chloride,2  and 
en  boil  100  parts  of  this  with  300  parts  of  nitric  acid  of 
.  gr.  1*313  and  200  parts  of  water  for  about  ten  hours  in  an 
paratus  connected  with  an  inverted  condenser,  until  the 

smell  of  benzyl  chloride  and  benzaldehyde  has  disappeared,  and 

the   liquid  solidifies  on  cooling  to  a  crystalline  mass,  no  oily 
rops  being  formed.3 
This  method,  according  to  A.  von  Rad,  is  not  adapted  for 

the  preparation  of  the  acid  on  the  large  scale ;  it  can,  however, 

be  readily  obtained  by   heating   benzotrichloride   or  benzenyl 

chloride  with  water  under  pressure  :  4 

C6H5.CC13  +  2H20  =  C6H5.C02H  +  3HC1. 

Since  it  is  difficult  to  prepare  pure  benzenyl  chloride,  the  acid 
obtained  always  contains  chlorine  substitution  products,  which 
adhere  to  it  very  obstinately. 

Espenschied  proposes  to  boil  benzenyl  chloride  with  milk  of 
lime  or  caustic  soda  and  whitening,  and  then  to  proceed  as  in  the 
preparation  of  benzaldehyde  from  benzal  chloride  (p.  136). 

1  Jahresb.  Chem.  1868,  459. 

2  Grimaux  and  Lauth,  Bull.  Soc.  Chim.  vii.  100. 

3  Lunge  and  Petri,  Bcr.  Deutsch.  Chem.  Ges.  x.  1275. 

4  Dingier 's  Polyt.  Journ.  ccxxxi.  538. 


156  AROMATIC  COMPOUNDS. 

Jacobsen  obtains  benzole  acid,  together  with  acetyl  chloride, 
by  heating  benzenyl  chloride  with  glacial  acetic  acid  and  some 
zinc  chloride : 

C6H5.CC13  +  2CH3.CO.OH  =  C6H5.CO.OH  +  2CH3.COCl  +  HC1. 

In  order  to  avoid  the  evolution  of  hydrochloric  acid,  which 
carries  off  acetyl  chloride  with  it,  half  of  the  acetic  acid  is 
replaced  by  zinc  acetate. 

Benzoic  acid  can  also  be  prepared  without  the  formation  of 
acetyl  chloride,  by  heating  benzenyl  chloride  with  a  little  acetic 
acid  and  zinc  acetate,  and  gradually  adding  the  amount  of  water 
necessary  for  the  formation  of  the  acid.1 

Since  benzaldehyde  is  now  manufactured,  it  can  readily  be 
employed  as  a  source  of  benzoic  acid. 

2096  Properties. — It  crystallizes  in  lustrous,  flat,  monoclinic 
plates  or  needles  ;  by  the  gradual  evaporation  of  its  solution  it  is 
obtained  in  larger  tablets,  which  however  are  always  thin,  while 
when  Guichard  allowed  a  mixture  of  benzoin  resin  and  carbon 
disulphide  to  stand  for  a  long  time,  tolerably  large  crystals 
were  formed,  which  had  exactly  the  appearance  of  crystals  of 
gypsum.2 

Benzoic  acid  has  a  sharp  acid  taste  and  produces  a  peculiar 
irritation  in  the  throat ;  it  melts  at  121 '4°,  and  boils  at  249° 
(Kopp),  but  volatilizes  at  100°,  and  sublimes  rapidly  at  140°. 
It  also  volatilizes  with  steam,  one  gramme  passing  over  with 
two  litres  of  water  (Nolting).  Its  vapour  has  an  aromatic,  pene- 
trating odour,  produces  coughing  and  attacks  the  eyes  violently, 
more  mildly  when  it  is  mixed  with  steam.  The  specific  gravity 
of  its  vapour  is,  according  to  Mitscherlich,  4'27 ;  according  to 
C.  and  V.  Meyer,  who  determined  it  in  diphenylamine  vapour,  it 
is  4'24,3  the  calculated  number  being  4*229. 

1,000  parts  of  water  dissolve  : 4 

at    0      10     20     30     40     50      60       70        80       90     100° 
170  2-10  2-90  410  5*55  775  11'55  1775  27'15  4075  5875 

parts  of  the  acid. 

100  parts  of  absolute  ether  at  15°  dissolve  31 '35  parts ;  100 
parts  of  40  per  cent,  alcohol,  41'62  parts ;  and  100  parts  of 

1  Ser.  Deutsch.  Chem.  Ges.  xiii.  2013. 

2  Ibid.  vi.  453.  3  Ibid.  xi.  2258. 
4  Bourgoin,  Ann.  Chim.  Phys.  [5]  xv.  168. 


SALYLIC  ACID.  157 


absolute  alcohol,  4G'68  parts  of  benzole  acid ; l  boiling  alcohol 
dissolves  about  twice  this  quantity.  It  also  readily  dissolves  in 
chloroform,  carbon  disulphide,  volatile  and  fatty  oils  and  con- 
centrated sulphuric  acid. 

It  is  characteristic  of  benzoic  acid  that  certain  impurities,  even 
when  they  are  present  in  extremely  small  quantities,  alter  its 
physical  properties  to  a  very  considerable  extent ;  so  largely  in 
fact,  that  the  impure  acid  has  been  mistaken  for  an  isomeride. 
Thus,  E.  Kopp,  by  the  oxidation  of  gum  benzoin  with  dilute 
nitric  acid,  obtained  the  amorphous  parabenzoic  acid  as  a  white 
powder,  which  melts  at  113°;  it  is  converted  into  ordinary 
benzoic  acid  by  distillation.2  Another  so-called  isomeric  acid 
named  salylic  acid  by  Lautemann  and  Kolbe,  because  they 
d  obtained  it  from  salicylic  acid,  C6H4(OH)COOH.3  The 
itter  was  converted  into  a  chlorine  compound  by  phosphorus 
>ntachloride  and  this  was  decomposed  by  water  into  hydro- 
iloric  acid  and  chlorosalylic  acid  or  orthochlorobenzoic  acid, 
C6H4C1.CO2H.  Salylic  acid  was  obtained  from  this  by  the 
action  of  water  and  sodium  amalgam.  This  compound  crystal- 
lizes from  hot  water  in  indistinct  needles  or  small  plates,  which, 
on  drying,  form  an  odourless  sandy  powder,  while  the  soft,  light 
ttes  of  benzoic  acid  have  a  faint  but  distinct  aromatic  odour. 
rhen  its  aqueous  solution  is  boiled,  however,  the  characteristic 
lell  becomes  perceptible.  It  melts  at  a  lower  temperature 
lan  benzoic  acid,  from  which  it  also  differs  in  fusing  when 
leated  with  a  quantity  of  water  insufficient  to  dissolve  it,  and  in 
fact  that  its  hot,  saturated  solution  becomes  milky  on 
)ling  and  then  again  clear,  crystalline  flocks  being  deposited, 
salts  also  differ  from  the  benzoates  in  crystalline  form  and 
solubility. 

Kekule  confirmed  these  results,4  and  Griess  obtained  a  substance 
which  he  found  to  be  identical  with  salylic  acid,  by  decomposing 
azo-amidobenzoic  acid  suspended  in  boiling  alcohol  with  nitrogen 
trioxide.5  Kolbe  and  Lautemann  put  forward  the  suggestion 
that  the  isomerism  of  these  acids  was  due  to  a  difference  be- 
tween their  radicals,6  but  Cannizzaro  showed  that  on  distillation 
with  caustic  baryta  they  both  yield  the  same  substance,  viz., 
benzene.7 

The  two  acids  were  then  assumed  to  be  physical  isomerides, 

1  Bourgoin  ;  Bull.  Soc.  Chim.  xxix.  242.         2  Compt.  Rend.  CMm.  1849,  154. 

Ann.  Cfam.  Pharm.  cxv.  187.  4  Ibid,  cxvii.  158. 

6  Ibid,  cxvii.  34.  6  Ibid.  cxv.  169.          *  Ibid.  Suppl.  i.  247. 


158  AROMATIC  COMPOUNDS. 

until  Reichenbach  and  Beilstein  showed  that  salylic  acid  is 
nothing  but  a  more  or  less  impure  benzoic  acid.1  If  the  acid  ob- 
tained from  salicylic  acid  be  subjected  to  distillation  with  steam, 
a  perfectly  pure  benzoic  acid  passes  over  which  possesses  the 
correct  melting-point  and  all  the  characteristic  properties.  Kolbe 
has  confirmed  this  result,  and  finds  that  his  salylic  acid  contains 
a  small  quantity  of  a  yellow,  resinous  substance,  which  is  not 
volatile  in  steam.  When  some  of  this  is  added  to  a  hot,  satu- 
rated solution  of  pure  benzoic  acid,  the  liquid  on  cooling  deposits 
crystals  of  salylic  acid.  The  admixed  substance  can  be  destroyed 
by  the  addition  of  potassium  permanganate  to  the  hot  solution.2 

The  salylic  acid  obtained  from  azo-amidobenzoic  acid  con- 
tains a  little  nitrobenzoic  acid,  as  does  the  benzoic  acid  which  is 
prepared  by  the  oxidation  of  toluene  with  dilute  nitric  acid.3 
When  this  acid  is  distilled,  a  trace  of  the  nitro-compound  vola- 
tilizes with  it  and  prevents  it  from  crystallizing  well,  while  when 
a  little  of  the  nitro-compound  is  added  to  a  hot  saturated  solution 
of  pure  benzoic  acid,  it  becomes  milky  on  cooling  and  deposits 
flocks,  which  are  much  more  soluble  than  the  pure  acid  and 
melt  at  a'  lower  temperature.  Pure  benzoic  acid  cannot  be 
prepared  from  this  either  by  sublimation  or  re-crystallization,  but 
the  impurity  can  readily  be  removed  by  dissolving  in  concentrated 
ammonia,  saturating  with  sulphuretted  hydrogen,  heating  to  boil- 
ing, and  then  evaporating  off  the  ammonium  sulphide  on  the 
water-bath.  Hydrochloric  acid  now  precipitates  pure  benzoic 
acid,  while  amidobenzoic  acid  remains  in  solution  (Reichenbach 
and  Beilstein). 

An  admixture  of  cinnamic  acid,  which  melts  at  133'3°,  also 
lowers  the  melting-point  of  benzoic  acid  considerably,4  so  that  a 
mixture  of  equal  parts  of  the  two  acids  melts  at  84'3°,  an  excess 
of  either  acid  raising  the  melting-point.5 

Benzoic  acid  is  employed  in  the  manufacture  of  colouring 
matters  and  in  medicine.  It  has  antiseptic  properties,  but 
exerts  a  more  feeble  action  than  salicylic  acid.6  The  observation 
that  cranberries  withstand  fermentation  and  putrefaction  better 
than  most  other  fruits,  gave  the  clue  to  the  discovery  of  benzoic 
acid  in  them. 

1  Ann.  Chem.  Pharm.  cxxxi.  309. 

2  Journ.  PraU.  Chem.  [2]  xii.  151. 

8  Fittig,  Ann.  Chem.  Pharm.  cxx.  214. 

4  Kolbe.  and  Lautermanu,  Ann.  Chem.  Pharm.  cxix.  136. 

5  Kachlar,  Ber.  Deutsch.   Chem.  Ges.  ii.  515. 

6  Kolbe  and  v.  Meyer,  Journ.  Prakt.  Chem.  [2]  xxii.  133,  178. 


DECOMPOSITIONS  OF  BENZOIC  ACID.  159 

2097  When  benzole  acid  is  distilled  with  slaked  lime  or 
caustic  baryta,  it  is  decomposed  into  benzene  and  carbon 
dioxide  (Mitscherlich).  It  also  undergoes  this  decomposition 
when  heated  with  caustic  soda,1  and  when  its  vapour  is  passed 
over  heated  pumice  stone  2  or  iron.3  Some  diphenyl  is  always 
formed  in  this  way,  and  at  a  very  high  temperature  the  acid  is 
decomposed  with  separation  of  graphite  and  formation  of  carbonic 
oxide,  carbon  dioxide,  hydrogen  and  diphenyl,  C19H10.4  When 
its  vapour  is  passed  over  heated  zinc-dust,  it  is  reduced  to  benz- 
aldehyde.5  Sodium  amalgam  reduces  its  boiling  solution  with 
formation  of  benzaldehyde,  benzyl  alcohol,  a  crystalline  com- 
pound, C14HUO2,  and  benzoleic  acid,  C7H10O2,6  which  is  further 
described  below.  On  heating  with  concentrated  hydriodic  acid 
to  275° — 280°,  it  is  first  reduced  to  toluene,  but  heptane  and 
hexane  are  formed  on  further  heating,  the  latter  being  derived 
from  the  benzene,  which  is  formed  by  the  decomposition  of  the 
acid.7 

It  is  not  attacked  by  chromic  acid  solution  ;  ozone  converts  it 
in  alkaline  solution  into  carbon  dioxide  and  water.8  It  is  con- 
verted in  the  animal  organism  into  hippuric  acid  and  appears 
in  this  form  in  the  urine  ; 9  a  portion  is  simultaneously  oxidized 
to  succinic  acid,  which  is  also  formed  when  an  aqueous  solution 
of  benzoic  acid  is  treated  with  lead  dioxide  and  sulphuric  acid.10 
On  oxidation  with  manganese  dioxide  and  sulphuric  acid,  Carius 
obtained  carbon  dioxide,  formic  acid,  and  some  phthalic  acid,11 
while  Oudemans  also  detected  a  small  quantity  of  the  isomeric 
terephthalic  acid.12  When  the  solution  of  its  calcium  salt  is 
electrolyzed,  the  acid  is  not  decomposed  in  a  similar  manner  to 
the  fatty  acids,  but  the  nascent  oxygen  exerts  an  oxidizing 
action,  with  formation  of  carbon  dioxide,  carbonic  oxide,  and 
some  acetylene.13 

Benzoleic  acid,  or  Hydrobenzoic  acid,  C7H1002,  is  formed  when 
sodium  amalgam  is  allowed  to  act  on  a  boiling  solution  of  benzoic 

I  Barth  and  Schreder,  Ber.  Deutsch.  Chem.  fte.s.  xii.  2555.  . 
-  Barreswill  and  Boudault,  Journ.  Pharm.  Chim.  v.  265. 

3  F.  d'Arcet,  Journ.  Prakt.  Cham.  xiii.  427. 

4  Schulz,  Ann.  Chem.  Pharm.  clxxiv.  202. 

5  Baeyer,  ibid.  cxl.  295. 

6  Kolbe,  ibid,  cxviii.  122  ;  Herrmann,  ibid,  cxxxii.  75. 

7  Berthelot,  Jahresb.  Chem.  1867,  364. 

8  Gorup-Besanez,  Ann.  Chem.  Pharm.  cxxv.  207. 

9  "Wohler,  BcrzeUus1  Lehrb.  Ed.  4,  iv.  376  ;  see  also  hippuric  acid. 
10  Meissner  and  Shepard,  Jahresb.  Chem.  1866,  397. 

II  Ann.  Chem.  Pharm.  cxlviii.  72. 

12  Zcitschr.  Chem.  1869,  84. 

13  Berthelot,  Bull.  Soc.  Chim.  [2]  ix.  103  ;  Bourgoin,  ibid.  431. 


160  AROMATIC  COMPOUNDS. 

acid,  hydrochloric  acid  being  added  at  intervals  benzyl  alcohol 
and  a  crystalline  substance,  C14H14O2,1  are  simultaneously  formed. 
Otto  obtained  the  same  acid  from  hydrobenzuric  acid,2  and, 
together  with  other  compounds,  by  the  action  of  sodium  amalgam 
on  benzoyl  glycollic  acid  (p.  165).3  It  is  an  oily  liquid,  which  has 
a  repulsive  odour  resembling  that  of  valerianic  acid,  and  is 
rapidly  altered  in  the  air.  When  hydrochloric  acid  is  passed 
into  its  alcoholic  solution,  the  ethyl  ether  is  formed  and  resembles 
ethyl  valerate,  but  has  a  sharper  smell ;  in  the  air  the  smell 
becomes  exceedingly  disagreeable,  and,  since  it  clings  persistently 
to  the  clothes,  increases  the  difficulty  of  the  investigation  of  the 
compound  and  the  free  acid. 


SALTS  AND  ETHERS  OF  BENZOIC  ACID. 

2098  Benzoic  acid  decomposes  carbonates  in  aqueous  solution, 
but  when  a  current  of  carbon  dioxide  is  passed  into  an  alcoholic 
solution  of  potassium  benzpate,  potassium  carbonate  separates 
out.  Most  of  the  benzoates  are  soluble  in  water  and  alcohol ; 
some,  such  as  the  sodium  and  barium  salts,  are  withdrawn  from 
their  solutions  by  animal  charcoal,  and  calcium  benzoate  is 
decomposed  by  it,  so  that  free  benzoic  acid  can  be  extracted  by 
ether.4 

Potassium  benzoate,  C7H5K02-f  3H20,  crystallizes  with  diffi- 
culty in  small  plates  which  effloresce  in  the  air  and  are  very 
soluble  in  water  and  alcohol. 

Sodium  benzoate,  C7H5NaO2  +  H20,  crystallizes  in  needles, 
which  also  effloresce  in  the  air  and  are  very  soluble  in  alcohol 
It  is  used  in  medicine. 

Ammonium  benzoate,  C7H5(NH4)O2,  separates  from  a  solution 
containing  an  excess  of  ammonia  in  deliquescent  rhombic 
crystals ;  it  is  also  employed  medicinally.  Large  crystals  of 
the  less  soluble  acid  salt,  C7H5(NH4)O2  +  C7H6O2,  are  obtained 
by  the  gradual  evaporation  of  its  aqueous  solution  (Berzelius). 

Calcium  benzoate,  (C7H5O2)2Ca  +  2H2O,  crystallizes  from  hot 
water  in  long  lustrous  needles  which  form  fascicular  aggregates ; 
they  dissolve  in  29  parts  of  cold  water  and  effloresce  in  the  air. 

1  Herrmann,  Ann.  Chem.  P7utrm.  cxxxii.  75, 

2  Ibid,  cxxxiv.  115.  3  Ibid.  cxlv.  350. 
*  L.  Liebermann,  Ber.   Wien.  Akad.  1877,  331. 


ETHYL  BENZOATE.  ir,l 


Barium  lenzoate,  (C7H5O2)2Ba  ~h  3H2O,  is  only  slightly  soluble 
in  water,  and  crystallizes  in  needles  or  hard,  lustrous  tablets. 

Lead  lenzoate,  (C7H6O2)2Pb  +  H2O,  is  obtained  by  the  addi- 
tion of  lead  acetate  to  a  solution  of  the  potassium  salt ;  it  is  a 
crystalline,  difficultly  soluble  precipitate. 

Copper  lenzoate,  (C7H5O2)2Cu+ 2H20,  crystallizes  in  light 
blue  plates  united  in  spherical  masses  or  in  needles. 

Silver  lenzoate,  C7H5Ag02,  is  a  curdy  precipitate,  which  is 
soluble  in  alcohol  and  crystallizes  from  hot  water  in  flat 
needles. 

Mercuric  lenzoate,  (C7H5O2)2Hg  +  H20,  crystallizes  from  hot 
rater  in  needles  which  are  almost  insoluble  in  cold  water. 

Ferric  lenzoate,  (C7H5O2)6Fe2.  Berzelius  obtained  this  salt  in 
yellow  needles  by  dissolving  ferric  hydroxide  in  aqueous  benzoic 
nd ;  it  is  decomposed  by  water  and  alcohol  with  formation 

an  insoluble  basic  salt.  Sestini  was  unable  to  prepare  this 
mipound.1  When  a  soluble  benzoate  is  added  to  neutral  ferric 
chloride,  a  reddish  yellow  precipitate  is  thrown  down,  which  is 
decomposed  by  washing  with  water  into  a  soluble  acid  salt  and 
an  insoluble  basic  salt.  If  the  iron  solution  has  been  previously 
treated  with  sufficient  ammonia  to  produce  a  dark  red  coloura- 
tion, soluble  benzoates  give  a  voluminous,  hydrated,  flesh-coloured 
precipitate  of  (C7H5O2)3Fe2(OH)3,  which  is  not  altered  by  cold 
water. 

These  reactions  are  employed  for  the  separation  of  iron  from 
iganese  and  for  the  detection  of  benzoic  acid  and  its  separa- 
tion from  other  acids. 

Methyl  lenzoate,  C6H5.CO.OCH3,  is  best  prepared  by  passing 
lydrochloric  acid  into  a  solution  of  benzoic  acid  in  methyl 
alcohol,  distilling,  and  then  precipitating  the  ether  with  water.2 
It  is  a  liquid  which  possesses  an  aromatic  odour  and  boils 
at  199°. 

Ethyl  lenzoate  was  prepared  by  Scheele  as  long  ago  as  1*785,  by 
the  distillation  of  a  mixture  of  alcohol,  benzoic  acid  and  hydro- 
chloric acid.  It  is  not  formed  when  an  alcoholic  solution  of  the 
acid  is  allowed  to  stand  in  the  cold,  but  the  ether  is  gradually 
formed  if  a  little  hydrochloric  acid  be  added,  or  if  the  liquid 
be  heated  to  100°.  In  order  to  prepare  it,  the  method  adopted 
for  the  preparation  of  the  methyl  ether  may  be  followed,  or  the 
alcoholic  solution  of  the  acid  may  be  heated  with  sulphuric  or 

1  Zeitschr.  Chem  iv.  668. 

2  Carius,  Ann.  Chem.  Pharm.  ex.  210. 


162  AROMATIC  COMPOUNDS. 

hydrochloric  acid.     It  is  a  liquid  which  has  a  pleasant  aromatic 
smell,,  and  boils  at  213°. 

Ethyl  benzoate  is  also  readily  formed  by  the  action  of  benzoyl 
chloride  on  alcohol  (Wohler  and  Liebig),  which  is  more  readily 
attacked  by  it  than  water.  The  presence  of  alcohol  even  in  very 
dilute  aqueous  solution  can  therefore  be  detected  by  warming  it 
with  a  little  benzoyl  chloride  and  removing  the  excess  of  this  by 
caustic  soda;  even  when  only  01  per  cent,  of  alcohol  is  present, 
the  characteristic  smell  of  ethyl  benzoate  can  be  distinctly 
recognized  (Berthelot ;  see  Part  I.  p.  318). 

Boiling-point. 

Isopropyl  benzoate,1  C6H5.CO.OCH(CH3)2  .  218° 
Propyl  benzoate,2  C6H5.CO.OC3H7  .  .  229'5° 

Butyl  benzoate,3  C6H5.CO.OC4H9  .  .  .  247-3° 
Amyl  benzoate,4  C6H5.CO.OC5Hn  .  .  .  260  7° 
Octyl  benzoate,5  C6H5.CO.OC8H17  .  .  .  306° 
Allyl  benzoate,6  C6H5.CO.OC3H5  .  .  .  228° 

Benzyl  benzoate,  C6H5.CO.OCH2.C6H5.  Cannizzaro  obtained 
this  compound  by  the  distillation  of  benzyl  alcohol  with  benzoyl 
chloride  or  benzoic  anhydride.7  It  boils  at  323° — 324°,  has  the 
sp.  gr.  of  1'1227  at  19°,  and  solidifies  in  a  freezing  mixture  to 
lustrous,  compact  crystals,  melting  at  21  °.8  As  already  mentioned, 
it  is  also  formed  by  the  action  of  sodium  methylate  on  benz- 
aldehyde  (p.  93)  and  is  a  constituent  of  Peru  balsam 9  and  of 
Tblu  balsam,10  but  has  not  yet  been  obtained  from  them  in  the 
pure  state.  If  the  ether  be  submitted  to  distillation  while  it  still 
contains  water,  it  is  decomposed  with  formation  of  benzoic  acid, 
benzyl  alcohol  and  toluene. 

Ethylene  benzoate,  (C6H5.CO2)2C2H4.  Wurtz  prepared  this 
compound  by  the  action  of  silver  benzoate  on  ethylene 
bromide  ; n  it  crystallizes  from  ether  in  lustrous,  rhombic  prisms,12 
melting  at  67°. 

1  Silva,  Ann.  Chem.  Pharm.  cliv.  255. 

2  Linnemann,  ibid.  clxi.  28. 

3  Ibid.  clxi.  92. 

*  Rieckher,  ibid.  Ixiv.  336. 

5  Zincke,  ibid.  clii.  7. 

6  Hofmann  and  Cahours,  ibid.  c.  358  ;  cii.  297. 

7  Ibid.  xc.  254. 

8  L  Claisen,  private  communication. 

9  Kraut,  Ann.  Ghcm.  Pharm.  clii.  129  ;  Ber.  Deutsch.  Chem.  Ges.  ii.  18. 

10  Busse,  ibid.  ix.  830. 

11  Jahresb.   Chem.  1859,  676. 

12  Bodewig,  ibid.  1879,  676. 


PHENYL  BENZOATE.  163 


The   following   propylene   ethers   have   been   prepared  in   a 

similar  manner  : 

Melting-point. 
Propylene  benzoate  :  1 
C6H5.CO.OCH2 

,  viscous  fluid    ..... 
C6H5.CO.OCH.CH3 
Trimethylene  benzoate  :  2 

scal?  crystals  ----     53° 

Dimethylmethylene  benzoate  :  3 


,  monoclinic  pyramids  .      69—71 


The  last  of  these  yields  acetone  on  saponification. 

Benzidcne  lenzoate,  (C6H5.CO.O)2CH.C6H5,  is  formed  by  the 
action  of  benzidene  chloride  on  silver  benzoate,  and  crystallizes 
in  transparent  prisms,  melting  at  50°.4 

The  benzoic  ethers  of  glycerol,  erythrol,  mannitol,  the  glucoses, 
etc.,  have  also  been  prepared.5 

2099  Phenyl  -lenzoate,  C6H5.CO.OC6H5.  Ettling  and  Sten- 
house  observed  a  compound  among  the  distillation  products  of 
copper  benzoate  which  they  named  benzoic  oxide,  C7H50,6  while 
Gerhardt  considered  it  to  be  the  radical  benzoyl.7  List  and 
Limpricht  then  found  that  it  has  the  formula  C13H1002,  and  is 
decomposed  by  alcoholic  potash  into  benzoic  and  carbolic  acids, 
so  that  it  is  a  compound  of  benzoic  acid  and  phenyl  oxide.8  They 
further  showed  that  it  is  identical  with  the  benzophenide,  which 
Laurent  and  Gerhardt  obtained  by  the  action  of  benzoyl  chloride 
on  phenol.9 

Phenyl  benzoate  is  readily  formed  when  benzoyl  chloride  is 
heated  with  phenol  until  hydrochloric  acid  ceases  to  be  evolved, 
and  also  when  phenol  is  heated  with  benzamide.10  It  is  readily 
soluble  in  alcohol  and  ether,  and  crystallizes  from  a  mixture  of 
these  in  lustrous,  monoclinic  prisms,11  which  melt  at  71°  and 
sublime  at  a  higher  temperature.  Its  smell  resembles  that  of 

1  Friedel  and  Crafts,  Zcitschr.  Chcm.  1871,  489  ;  Mayer,   Ann.  Chcm.  Pharm. 
cxxxiii.  255. 

2  Reboul,  Ann.  Chim.  Phys.  [5]  xiv.  500. 

3  Oppenheim,  Ann.  Chcm.  Pharm.  Suppl.  vi.   360  ;  Friedel  and  Ladenburg, 
ibid.  cxlv.  195. 

4  Engelhardt,  Jahresber.  Chem.  1857,  471  ;  Wicke,  Ann.  Chcm.  Pharm.  cii.  356. 

5  Berthelot,  ibid.   Ixxxviii.   311  ;  xcii.  302  ;  Jahresber.  1855,  677  ;  1856,  660  ; 
1860,  509. 

6  Ann.  Chcm.  Pharm.  liii.  77,  94.  7  Ibid.  Ixxxvii.  162. 

8  Ibid.  xc.  190.  9  Ibid.  Ixxv.  75  ;  Ixxxvii.  161. 

10  Guareschi,  ibid,  clxxi.  141.  "  Bodewig,  Jahresber.  1879,  675. 


1G4  AROMATIC  COMPOUNDS. 

the  geranium.  Chlorine  and  bromine  effect  substitution  in 
the  phenyl  and  not  in  the  benzoyl  group. 

Trinitrophenyl  bcnzoate,  C6H5.CO.OC6H2(NO2)3,  Gerhardt 
and  Laurent  prepared  this  compound  by  heating  picric  acid  with 
benzoyl  chloride.  It  is  insoluble  in  water,  slightly  soluble  in 
cold,  more  readily  in  hot  alcohol,  and  crystallizes  in  lustrous, 
golden-yellow,  rhombic  plates,  which  detonate  when  heated.1 

Cresyl  benzoate,  C6H5.CO.OC6H4.CH3.  The  three  isomeric 
ethers  have  been  prepared  by  Engelhardt  and  Latschinow.2 

Melting-  Boiling- 

point,  point. 

Orthocresyl  benzoate,  oily  liquid   ...      — 

Metacresyl  benzoate,  crystals     ....      38°         290° — 300° 
Paracresyl  benzoate,  six-sided  tablets    .      70° 

Phenylene  benzoate,  (C6H5.CO.O)2C6H4,  is  also  known  in  three 
isomeric  forms,  which  are  obtained  from  the  dihydroxybenzenes. 

Melting-point. 
Dibenzoylcatechol,  rhombic  crystals3    .    .    . 

Dibenzoylresorcinol,  scales 4 117° 

Dibenzoylquinol,  silky  needles  5 199° 

Tribenzoylphloroglucinol,  (C6H5.CO.O)3C6H3,  forms  small,  lus- 
trous scales,  which  are  almost  insoluble  in  alcohol.6  The  benzoic 
ether  of  pyrogallol,  according  to  Malin,  does  not  crystallize,  but 
its  dimethyl  ether,  and  two  homologues  of  the  latter  which 
occur  in  the  higher  boiling  portions  of  beech-wood-tar  oil,  give 
very  characteristic  ethereal  salts  of  benzoyl.7  Since  these  three 
ethereal  salts,  which  are  very  similar  in  their  properties,  can  be 
separated  by  means  of  their  different  solubilities,  they  will  be 
mentioned  here  : 

Melting-point. 

Benzoylpyrogallol  dimethyl  ether : 

C6H5.CO.OC6H3(OCH3):! 118° 

Benzoylmethylpyrogallol  dimethyl  ether : 

C6H5.CO.OC6H2(CH3)(OCH3)2  .    .    .    .          118°— 119° 
Benzoylpropylpyrogallol  dimethyl  ether : 

C6H5.CO.OC6H2(C3H7)(OCH3)2    ...  91° 

1  Ann.  Chem.  Pharm.  Ixxv.  77. 

-  Zcitschr.    Chem.  1869,  615  ;  see  also  Kekule,  Ber.  Dcutsch.  Chem.  Ges.  vii. 
1007  ;  Guareschi,  Ann.  Chem.  Pharm.  clxxi.  142. 

3  Nachbauer,  ibid.  cvii.  243. 

*  Malin,  ibid,  cxxxviii.  76  ;  Dobner,  Bcr.  Dcutsch.  Chem.  Gcs.  xi.  2269. 

5  Dbbner  and  Wolft',  ibid.  xii.  661. 

6  Hlasiwetz  and  Pfuundler,  Ann.  Chem.  Pharm.  cxix.  199. 

7  Hofmann,  Ber.  Lcutsch.  Chem.  Ges.  xii.  1373. 


BENZOYL-LACTIC  ACID.  165 

Quinonoxime  benzoate,  C6H4O(NO.CO.C6H5),  is  formed  when 
benzoyl  chloride  is  added  to  sodium  quinonoximate  (Part  III. 
p.  172),  which  is  covered  with  pure  ether  or  chloroform.  It 
crystallizes  in  yellowish  needles,  which  melt  with  decomposition 
at  168° — 175°,  and  give  Lieberrnann's  reaction  with  phenol  and 
sulphuric  acid.1 

2100  Benzoyl- gly collie  acid,  C6H5.CO.OCH2.C02H,  has  hitherto 
only  been  prepared  from  hippuric  acid  or  benzoylamido-acetic 
acid,  by  treating  it  with  nitrous  acid,2  or  by  passing  chlorine 
into  its  dilute  alkaline  solution.3  It  crystallizes  from  hot  water 
in  thin  tablets  or  large  prisms,  and  decomposes  on  boiling  with 
water,  or  more  rapidly  with  dilute  mineral  acids,  into  benzoic 
and  glycollic  acids.  Otto,  by  the  action  of  sodium  amalgam  on 
its  aqueous  solution,  obtained  benzoleic  acid  (p.  159)  and  two 
other  isomeric  acids  which  have  not  yet  been  thoroughly 
investigated. 

Ethyl  lenzoyl-glycollate,  C6H5.CO.OCH2.C02C2H5.  Andrejew 
obtained  this  substance  by  heating  ethyl  chloracetate  with 
sodium  benzoate ;  it  is  a  liquid  which  boils  at  277° — 279°,  and 
decomposes  into  alcohol,  benzoic  acid  and  glycollic  acid,  when 
boiled  with  alcoholic  potash.4 

Benzoyl-lactic  acid,  CH3(CH.O.CO.C6H5)C02H,  is  formed 
when  lactic  acid  is  heated  to  180°  with  benzoic  acid,5  as  well  as 
by  the  action  of  benzoyl  chloride  on  lactic  acid  or  calcium  lac- 
tate.6  It  separates  from  a  hot,  aqueous  solution  in  tablets  or 
needles,  melting  at  112°.  On  boiling  with  water  or  a  dilute 

id  it  is  decomposed  into  lactic  and  benzoic  acids. 

Ethyl  lenzoyl-lactate,  C10H9O4.C2H5,  is  formed  by  the  action  of 
oyl  chloride  on  ethyl  lactate,  and  by  heating  silver  benzoyl- 
lactate  with  ethyl  iodide.  It  is  a  liquid  which  boils  at  288°, 
and  is  decomposed  into  lactic  acid  and  ethyl  benzoate  by  heating 
with  water  to  150°. 

Benzoyl  compounds  of  tartaric  and  racemic  acids  have  also 
been  prepared.7 

1  Walker,  Per.  Deutsch.  Chem.  Ges.  xvii.  399. 

2  Strecker,  Ann.  Chem.  Pharm.  Ixviii.  54  ;  Strecker  and  Sokolow,  ibid.  Ixxx. 

3  Gbssmann,  ibid.  xcix.  181.  *  Ibid,  cxxxiii.  284. 
Strecker  and  Sokolow,  loc.  cit.  ;  Strecker,  ibid.  xci.  359. 

6  Wislicenus,  ibid,  cxxxiii.  264. 

7  Dessaignes,  Jahresber.  1857,  307  ;  Perkin,  Ann.    Chem.  Pharm.  Suppl.  v. 
2/4  ;  Anschiitzand  Pictet,  Ber.  Deutsch.  Chem.  Ges.  xiii.  1178. 

242 


166  AROMATIC  COMPOUNDS. 


OXIDES  OF  BENZOYL. 

2101  Benzoyl  oxide,  or  Benzoic  anhydride,  (C6H5.CO)20,  was 
discovered  by  Gerhardt  in  1853.  He  first  prepared  it  by  heating 
benzoyl  chloride  with  sodium  benzoate,  and  named  it  anhydrous 
benzoic  acid  or  benzoyl  benzoate  ; l  he  subsequently  found  that  it 
can  be  more  simply  obtained  by  the  action  of  phosphorus  oxy- 
chloride  on  an  excess  of  sodium  benzoate,  a  portion  of  this 
being  simultaneously  converted  into  benzoyl  chloride.2  Phos- 
phorus pentachloride  3  or  chloride  of  sulphur  4  may  be  employed 
instead  of  phosphorus  oxychloride.  It  is  also  formed  in  small 
quantity  when  benzoic  acid  is  heated  with  phosphorus  pent- 
oxide,6  and  in  larger  amount  by  heating  benzoyl  chloride  to 
140°— 150°  with  barium  oxide,6  or  to  160°— 220°  with  benzoic 
acid.7  Gerhardt  had  already  found  that  it  may  easily  be  ob- 
tained by  the  action  of  benzoyl  chloride  on  potassium  oxalate  : 

K2C204  +  2C6H5.COC1  =  (C6H5.CO)20  +  2KC1  +  CO  +  C02, 

Anhydrous  oxalic  acid  may  be  advantageously  employed  instead 
of  the  potassium  salt ;  the  reaction  takes  place  at  50° — 60°  ac- 
companied by  a  regular  evolution  of  gas,  and  80  per  cent,  of  the 
theoretical  yield  is  obtained,  together  with  some  unattacked 
chloride  and  benzoic  acid.8  Finally,  it  can  also  be  obtained  by 
heating  benzenyl  trichloride  with  silver  oxide,  or  with  concen- 
trated sulphuric  acid  containing  4'6  per  cent,  of  water  : 9 

C6H6.COX 
2C.H..CCL  +  3H00  =  >O  +  6HC1. 

C6H6.CO/ 

Anhydrous  oxalic  acid  may  be  substituted  for  the  sulphuric 
acid  : 10 

2C6H5.CC13  +  3C204H2  =  (C6H5.CO)20  +  3HC1  +  SCO  +  3CO,. 

Ann.  Chem.  Pharm.  Ixxxii.  127.  2  Ibid.  Ixxxvii.  73. 

Wunder,  Journ.  Prakt.  Chem.  Ixi.  280. 
Heintz,  Pogg.  Ann.  xcviii.  458. 
Etard  and  Gal,  Bull.  Soc.  Chim.  xxv.  342. 
Gal,  Ann.  Chem.  Pharm.  cxxviii.  127. 
Anschiitz,  Ber.  Deutsch.  Chem.  Ges.  x.  1882. 
Ibid. 

Janssen,  ibid.  xii.  1495,  Patent  30  Oct.  1878  (No.  6689). 
10  Anschiitz,  ibid,  ccxxvi.  20. 


BENZOIC  ANHYDRIDE.  167 


Benzoic  anhydride  crystallizes  in  rhombic  prisms  (Bodewig), 
melting  at  42° ;  it  boils  at  360°  (Anschutz),  and  is  tolerably 
soluble  in  alcohol  and  ether.  It  is  scarcely  attacked  by  cold 
water,  but  when  heated  with  water  it  gradually  forms  benzoic 
acid,  and  with  alcohol,  ethyl  benzoate.  When  heated  in  a 
stream  of  hydrochloric  acid,  it  decomposes  into  benzoyl  chloride 
and  benzoic  acid.1  Chlorine  and  bromine  exert  a  similar  action, 
substitution  products  being  simultaneously  formed. 

Benzoyl  acctyl  oxide,  CH3.CO.O.CO.C6H5.  Gerhardt  prepared 
this  compound  by  the  action  of  acetyl  chloride  on  sodium 
benzoate,  and  named  it  anhydrous  benzoic  acetic  acid.2  It  is 
a  heavy,  oily  liquid,  which  has  a  pleasant  smell  like  that  of 
Spanish  wine,  is  gradually  attacked  by  water,  more  rapidly  by 
alkalis,  and  is  completely  decomposed  by  distillation  into  benzoic 
anhydride  and  acetic  anhydride.3  It  is  also  formed  when  ben- 
zoic acid  is  heated  to  220°  with  acetic  anhydride.4  According  to 
Loir,  an  anhydride  is  obtained  by  the  action  of  benzoyl  chloride 
on  sodium  acetate,  which  differs  from  that  prepared  by  Gerhardt's 
method  in  yielding  acetyl  chloride  when  heated  with  hydro- 
chloric acid  to  130°,  while  Gerhardt's  compound  is  first  attacked 
at  160°,  with  formation  of  benzoyl  chloride.5  This,  however,  is 
inaccurate,  and  Greene  has  shown  that  the  compound,  in  what- 
ever way  it  is  prepared,  behaves  in  exactly  the  same  manner 
towards  hydrochloric  acid,  the  same  products — acetyl  chloride  and 
acetic  acid,  benzoyl  chloride  and  benzoic  acid — being  formed  as 
in  the  case  of  the  anhydrides  themselves.6 

A  number  of  other  mixed  anhydrides  are  now  known,  which, 
like  the  foregoing,  decompose  on  distillation  into  benzoic  an- 
hydride and  another  simple  anhydride,7  and  must  therefore  be 
looked  upon  rather  as  mixtures  than  definite  compounds. 

Benzoyl  dioxide,  or  Benzoyl  peroxide,  (C6H5.CO)2O2,  was  prepared 
by  Brodie  by  the  action  of  benzoyl  chloride  on  barium  dioxide ; 
it  separates  from  ether  or  carbon  disulphide  in  rhombic  crystals, 
which  melt  at  103-5°,  detonate  when  more  strongly  heated,  and 
when  boiled  with  caustic  potash  are  converted  into  benzoic  acid 
with  evolution  of  oxygen.8 

1  Mosling,  Ann.  Chcm.  Pharm.  cxviii.  303.  2  Ibid.  Ixxxvii.  81. 

3  Anschiitz,  ibid,  ccxxvi.  12.  *  Ibid. 

8  Ann.  Chim.  Phys.  [5]  xviii.  132. 

6  Bull.  Soc.  Chim.  xxxiii.  424. 

7  Gerhardt,   Ann.    Chcm.  Pharm.   Ixxxii.   127  ;  Ixxxvii.   163  ;  Chiozza,   ibid. 
Ixxxiv.  106  ;  Ixxxvi.  259  ;  Chiozza  and  Malerba,  ibid.  xci.  102. 

8  Ann.  Chcm.  Pharm.  cviii.  80  ;  Lippmann,  Monatsh.  Chem.  v.  560. 


1G8  AROMATIC  COMPOUNDS. 


HALOGEN  COMPOUNDS  OF  BENZOYL. 

2102  Benzoyl  chloride,  C6H5.COC1,  was  discovered  in  1832  by 
Wohler  and  Liebig ;  they  obtained  it  by  the  action  of  dry 
chlorine  on  pure  oil  of  bitter  almonds,  and  describe  it  as  a  trans- 
parent liquid  the  vapour  of  which  violently  attacks  the  eyes,  and 
has  a  peculiar,  very  penetrating  odour  resembling  the  sharp  smell 
of  horse-radish.1  Cahours  then  prepared  it  by  the  action  of 
phosphorus  pentachloride  on  benzoic  acid,2  Gerhardt  by  that  of 
phosphorus  oxychloride  on  sodium  benzoate,3  and  Bechamp  by 
heating  benzoic  acid  with  phosphorus  trichloride.4  Friedel  sub- 
sequently observed  its  formation  when  hydrochloric  acid  is  passed 
over  a  mixture  of  benzoic  acid  and  phosphorus  pentoxide  heated 
to  2000,5  this  being  an  important  general  method  for  the  forma- 
tion of  acid  chlorides.  Harnitz-Harnitzky  stated  that  it  might 
also  be  obtained  by  exposing  a  mixture  of  carbonyl  chloride  and 
benzene  vapour  to  the  action  of  sunlight,6  but  Berthelot  was 
unable  to  confirm  this  statement,7  although  it  is  undoubtedly 
formed  in  this  way  when  aluminium  chloride  is  present, 

(P.  soy 

It  also  may  be  obtained  by  heating  benzenyl  trichloride  with 
anhydrous  oxalic  acid : 

C6H5.CC13  +  C20,H2 = C6H5.COC1 + 2HC1+C02+CO. 

Benzoic  anhydride  is  also  formed  in  this  reaction.  In  order 
to  prepare  the  chloride,  a  mixture  of  two  molecules  of  phosphorus 
trichloride  with  three  molecules  of  benzoic  acid  is  heated  until 
hydrochloric  acid  ceases  to  be  evolved,  water  is  then  added  and 
the  oily  liquid  which  separates  purified  by  distillation ;  accord- 
ing to  another  method,  benzoic  acid  is  heated  with  one  molecule 
of  phosphorus  pentachloride,  and  the  mixture  distilled,  the  dis- 
tillate consisting  at  first  of  phosphorus  oxychloride  mixed  with 
a  little  benzoyl  chloride,  followed  by  pure  benzoyl  chloride.  The 
phosphorus  oxychloride  is  then  employed  for  a  further  prepara- 
tion by  being  heated  with  sodium  benzoate,  an  excess  of  which 

1  Monatsh.  Chcm.  iii.  262. 

2  Ibid.  Ix.  251.  3  Ibid  ixxxvii.  63. 

4  Journ.  Prakt.  Chcm.  Ixviii.  489.  6  Bull.  Soc.  Chim.  ii.  80. 

6  Ann.   Chcm.  Pharm.  cxxxii.  72.  7  Bull.  Soc.  Chim.  xiii.  9,  392. 

8  Ador,  Crafts  and  Friedel,  Ber.  Dcutsch.  Chem.  Gcs.  x.  1854. 


BENZOYL  CHLORIDE.  169 

must  be  avoided,  as,  otherwise,  some  benzoic  anhydride  would 
be  formed.  The  crude  chloride,  prepared  by  either  of  these 
methods,  is  freed  from  adhering  chlorides  of  phosphorus  by 
treatment  with  cold  water,  and  is  then  purified  by  distillation. 

Properties.  —  It  is  a  strongly  refractive  liquid,  which  fumes  in 
the  air,  has  a  sp.  gr.  of  1'2324  at  0°  and  solidifies  when  cooled  in 
crystals  melting  at  — 1°.  It  boils  at  198° ;  its  vapour  attacks 
the  lungs  and  mucous  membrane  very  violently.  It  is  gradually 
decomposed  by  cold,  more  rapidly  by  hot  water,  with  formation 
of  benzoic  and  hydrochloric  acids ;  it  is  rapidly  converted  into 
ethyl  benzoate  by  alcohol,  and  the  other  alcohols  produce  a 
similar  reaction.  Since  it  undergoes  double  decomposition  so 
readily,  it  is  largely  employed  for  the  preparation  of  other 
benzoyl  derivatives ;  many  examples  of  this  have  been  already 
given  and  others  will  be  met  with  in  the  sequel.  It  is  also 
employed  to  a  considerable  extent  in  the  same  way  as  acetyl 
chloride,  for  determining  the  number  of  hydroxyl  groups  con- 
tained in  carbon  compounds. 

Gerhardt  and  Laurent  found  that  the  compound  C6H5.CHO  -f 
C6H5.COC1  is  formed  by  the  action  of  chlorine  on  benzaldehyde  ; 
this  substance  is  insoluble  in  cold  alcohol,  crystallizes  in  lustrous 
plates,  is  decomposed  by  distillation  into  its  components,  and  by 
boiling  with  water  into  hydrochloric  acid  and  benzaldehydo- 
benzoic  acid ; 1  the  latter  compound  corresponds  to  the  ethidene- 
chloracetin  (Part  II.  p.  72)  obtained  in  a  similar  manner  from 
acetaldehyde,  and  is,  therefore,  lenzidene  lenzochlorohydrin  : 


C6H6.CHc 


Benzoyl  'bromide,  C6H5.COBr.  Wohler  and  Liebig,  by  the 
action  of  bromine  on  oil  of  bitter  almonds,  obtained  a  crystalline 
compound  which  they  looked  upon  as  beiizoyl  bromide.  This 
substance  was  subsequently  shown  by  Claisen  to  be  benzidene- 
benzobromohydrin  ;  this  chemist  then  prepared  benzoyl  bromide 
by  heating  three  molecules  of  benzoic  acid  with  two  molecules 
of  phosphorus  tribromide  ;  it  is  a  transparent,  colourless  liquid, 
has  an  odour  resembling  that  of  the  chloride,  but  fumes  more 
strongly  in  the  air,  is  more  readily  attacked  by  water  and  boils  at 
218°—  2190.2  It  combines  with  benzaldehyde  to  form  the  corn- 

1  Jahresber.  Chcm.  1850,  489.  2  Ber.  Dcutsch.  Chem.  Gcs.  xiv.  2473. 


170  AROMATIC  COMPOUNDS. 

pound  just  mentioned,  benzidcne  benzobromohydrin  or  bromo- 
bcnzylbenzoatc,  C6H5.CHBr.O.CO.C6H5,  which  crystallizes  from 
boiling  petroleum  ether  in  short  prisms  or  thick  tablets,  which 
melt  at  69° — 70°  and  are  decomposed  by  distillation  into  their 
components.  Paterno  obtained  the  same  compound,  together 
with  ethyl  bromide,  benzyl  bromide  and  benzaldehyde,  by  the 
action  of  bromine  on  ethyl  benzoate,  but  considered  it  to  be 
benzoyl  bromide.1 

Benzoyl  iodide,  C6H5.COI.  Wohler  and  Liebig  obtained  this 
compound  by  heating  the  chloride  with  potassium  iodide  as  a 
colourless,  foliated,  crystalline  mass,  which  readily  melts,  a  little 
iodine  being  set  free,  has  a  penetrating  odour  and  is  decom- 
posed by  water  and  alcohol.  It  has  not  been  analyzed. 

Benzoyl  fluoride,  C6H5.COF.  Borodin  prepared  this  compound 
by  the  distillation  of  the  chloride  with  acid  potassium  fluoride, 
F2HK,  in  a  platinum  retort.  It  is  a  heavy,  oily  and  colourless 
liquid,  which  boils  at  161 '5°,  has  a  still  more  powerful  odour 
than  the  chloride,  and  is  decomposed  by  water  into  benzoic  and 
hydrofluoric  acids.2 


SULPHUR  COMPOUNDS  OF  BENZOYL. 

2103  Thiobenzoic  acid,  C6H5.CO.SH.  Cloez  obtained  salts  of 
this  acid  by  the  action  of  benzoyl  chloride  on  .potassium  sulphide 
and  double  decomposition  of  the  potassium  thiobenzoate  thus 
formed  with  other  metallic  salts.3  The  compound  which  he 
separated  from  the  potassium  salt  and  looked  upon  as  thio- 
benzoic  acid  proved  to  be  benzoyl  disulphide.  The  free  acid  is 
obtained  by  decomposing  the  potassium  salt  with  dilute  hydro- 
chloric acid ;  a  yellow  liquid,  smelling  of  sulphur  compounds, 
separates  out  and  soon  solidifies  to  a  crystalline  mass,  melting  at 
24°,  which  decomposes  on  distillation  but  is  volatile  with  steam. 
It  is  readily  oxidized  to  benzoyl  disulphide,  this  action  taking 
place  even  when  its  alcoholic  solution  is  evaporated  in  the  air.4 

Potassium  thiobenzoate,  C6H5.CO.SK,  crystallizes  from  alcohol 
in  yellowish  tablets  or  prisms,  and  is  very  readily  soluble  in 
water.  The  silver  salt  is  a  yellowish  white,  and  the  lead  salt  a 

1  Gaz.   Chim.  Ital.  i.  586.  3  Ann  Chcm.  Pharm.  cxxvi.  60. 

3  Ibid.  cxv.  27. 

4  Engelhardt,  Latschinow  and  Malyschew,  ZcUsclir.  Chcm.  1868,  353. 


THIOBENZOIC  ACID. 

ite  precipitate ;  both  of  these  readily  blacken  and  decompose. 

)pper  sulphate  gives  a  greenish  yellow  precipitate  which  after 
time  becomes  red  and  then  contains  benzoyl  disulphide  : 
ic  chloride  yields  a  violet-brown  precipitate  which  becomes 

low  on  warming. 

Ethyl  thiobenzoate,  C6H5.CO.SC2H5,  is  formed  by  the  action  of 
benzoyl  chloride  on  lead  mercaptide,  Pb(SC2H5)2,1  and  of  ethyl 
iodide  on  silver  thiobenzoate.  It  is  a  yellow,  repulsive  smell- 
ing liquid,  which  boils  at  242°— 243°  and  is  decomposed  by 
saponification  with  caustic  potash  into  ben  zoic  acid  and  ethyl 
hydrosulphide,  while  potassium  hydrosulphide  yields  the  latter 
compound  and  thiobenzoic  acid.  It  is  oxidized  by  potassium 
permanganate  and  dilute  sulphuric  acid  to  benzoic  acid  and 
ethylsulphonic  acid.2 

Phenyl  thiobenzoate,  C6H5.CO.SC6H5,  is  obtained  by  heating 
benzoyl  chloride  with  phenyl  hydrosulphide.3  It  crystallizes 
from  alcohol  or  benzene  in  long  lustrous  needles,  melting  at  56°. 

Benzyl  thiobenzoate,  C6H5.CO.S.CH2.C6H5,  is  readily  soluble 
in  alcohol  and  benzene,  and  forms  lustrous,  asymmetric  crystals, 
melting  at  39'5°.  Its  behaviour  towards  reagents  resembles  that 
of  the  ethyl  ether.4 

Benzoyl  sulphide,  or  Thiobenzoic  anhydride,  (C6H5.CO)2S,  was 
obtained  by  Wohler  and  Liebig  in  an  impure  condition  by  the 
distillation  of  benzoyl  chloride  with  lead  sulphide.  It  is  pre- 
pared by  treating  potassium  thiobenzoate  with  benzoyl  chloride 
(Engelhardt,  Latschinow  and  Malyschew).  It  crystallizes  from 
ether  in  large  prisms,  which  melt  at  48°  and  decompose  on 
distillation.  When  heated  with  ammonia  it  yields  benzamide 
and  thiobenzoic  acid  ;  the  latter  is  also  formed  by  the  action  of 
potassium  hydrosulphide,  while  benzoic  acid  is  obtained  in 
addition  when  caustic  potash  is  employed. 

Benzoyl  disulphide,  (C6H5.CO)2S2,  is  formed  by  the  oxidation 
of  thiobenzoic  acid  and  by  heating  benzoic  anhydride  in  a  stream 
of  dry  sulphuretted  hydrogen.5  It  is  prepared  by  adding  a 
solution  of  iodine  in  potassium  iodide  to  an  aqueous  solution  of 
potassium  thiobenzoate.  It  is  only  slightly  soluble  in  alcohol 
and  ether,  and  crystallizes  from  hot  carbon  disulphide  in  large 


1  Tiitschew,  Jahresbcr.  Chcm.  1863,  483. 

2  Beckmann,  Journ.  Prakt.  Chcm.  [2]  xvii.  463. 

3  Schiller  and  Otto,  Ber.  Deutsch.  Chcm.  Gcs.  ix.  1635. 

4  Liiders  and  Otto,  ibid.  xiii.  1285. 

5  Mosliug;  Ann.  Chcm.  Pharm.  cxviii.  304. 


172  AROMATIC  COMPOUNDS. 

prisms   or   six-sided  tablets  which   melt  at  128°,  and   become 
coloured  violet-red  at  a  slightly  higher  temperature. 

Dithidbcnzoic  acid,  C6H5.CS.SH,  is  formed  in  small  quantity 
when  benzoyl  chloride  is  heated  with  lead  sulphide.  It  is  more 
easily  obtained  by  treating  benzenyl  trichloride  with  a  very 
dilute  alcoholic  solution  of  potassium  sulphide  : : 

C6H5.CC13  +  2K2S  =  C6H6.CS.SK  +  3KC1. 

Acetate  of  lead  first  precipitates  lead  sulphide  from  the 
solution  obtained,  and  then  the  lead  salt  of  the  acid,  which  is 
finally  decomposed  by  hydrochloric  acid.  It  is  a  dark  violet-red, 
heavy,  oily  liquid,  which  gives  a  carmine-coloured  solution  in 
ether-,  and  rapidly  forms  a  resinous  mass  when  exposed  to 
the  air. 

Lead  dithiolenzoate,  (C6H5.CS2)2Pb,  is  a  vermilion-coloured 
precipitate,  which  crystallizes  from  boiling  xylene  in  fine,  red 
needles. 

Benzoyl  thiocyanate,  C6H5.CO.S.CN,  is  obtained  by  the  action 
of  benzoyl  chloride  on  lead  thiocyanate  in  the  cold.  It  is  a 
yellow  liquid  which  has  a  penetrating  odour  resembling  that  of 
bitter  almonds,  and  can  only  be  distilled  without  'decomposition 
in  a  vacuum.2  It  combines  with  ammonia,  forming  benzoyl 
thiocarbamide,  (C6H6.CO)HN.CS.NH2,  and  is,  therefore,  probably 
benzoyl  mustard  oil,  C6H5.CO.N.CS. 


NITROGEN  COMPOUNDS  OF  BENZOYL. 

2104  Benzamide,  C6H&.CO.NH2.  Wohler  and  Liebig  obtained 
this  compound  by  the  action  of  benzoyl  chloride  on  ammonia, 
and  Fehling  subsequently  prepared  it  by  boiling  hippuric  acid 
with  water  and  lead  dioxide.3  Dumas  found  that  it  is  also 
formed  when  ethyl  benzoate  is  brought  into  contact  with  aqueous 
ammonia,  the  reaction  taking  place  more  rapidly  when  the 
mixture  is  heated  to  100.°*  It  is  also  formed  by  a  similar 
reaction  from  benzoic  anhydride.5 

1  Engelhardt  and  Latsehinow,  Zeitschr.   Chcm.  1868,  456  ;  see  also  Fleischer, 
Ann.  Chem.  Pharm.  cxl.  240. 

2  Miquel,  Ann.  Chim.  Phys.  [5]  xi.  300. 

3  Fehling,  Ann.  Chem.  Pharm.  xxv.  48  ;  Schwarz,  ibid.  Ixxv.  195. 
*  Compt.  Rend.  xxv.  734. 

5  Scheitz,  Marsh  and  Geuther,  Zeitschr.  Chem.  1868,  302. 


BENZAMIDE.  173 


In  order  to  prepare  it,  benzoyl  chloride  is  triturated  with  solid 
ammonium  chloride,  the  product  washed  with  cold  water,  and 
crystallized  from  hot  water  or  alcohol ; 1  or  equal  molecules  of 
benzoic  acid  and  ammonium  thiocyanate  may  be  heated  to  150° 
—170°,  carbonyl  sulphide,  ammonia,  sulphuretted  hydrogen  and 
carbon  dioxide  being  evolved,  while  benzamide  remains  behind 
and  only  requires  to  be  freed  from  benzoic  acid  by  washing  with 


imonia.2 


It  is  slightly  soluble  in  cold,  more  readily  in  hot  water, 
illy  when  it  contains  ammonia,  and  dissolves  readily  in 
>th  alcohol  and  ether.  When  its  aqueous  solution  is  rapidly 
cooled,  it  separates  out  in  small  plates,  while  on  more  gradual 
cooling  it  is  deposited  in  fine  needles,  which  gradually  change 
into  larger  crystals.  The  latter  are  also  obtained  by  allowing  a 
mixture  of  ethyl  benzoate  and  ammonia  to  stand,  or  by  gradually 
cooling  the  fused  compound ;  they  consist  of  well-formed,  mono- 
clinic  tablets,3  melting  at  1280.4  It  boils  at  286°— 290°,  a  small 
portion  being  decomposed  into  water  and  benzonitril,  C6H5.CN. 
The  latter  compound  may  be  readily  prepared  from  it  by  simply 
heating  with  a  dehydrating  agent ;  Wdhler  and  Liebig  had 
observed  that  when  heated  with  caustic  baryta,  an  oily,  aromatic 
liquid  having  a  sweet  taste,  was  formed,  and  that  it  might  also 
be  obtained  by  passing  the  vapour  of  the  compound  through  a 
red-hot  tube.  This  substance  was  afterwards  recognized  as  the 
izonitril  discovered  by  Fehling  in  the  year  1844.5 
Benzamide  is  not  decomposed  by  heating  with  dilute  alkalis : 
len  it  is  boiled  with  strong  caustic  potash  or  hydrochloric  acid 
decomposes  into  ammonia  and  benzoic  acid,  and  on  boiling 
rith  phenol,  ammonia  and  phenyl  benzoate  are  formed.6  When 
ited  with  ethyl  nitrite  to  120°,  the  following  reaction  takes 
)lace ; 7 

06H5.CO.NH2 + NO.OC2H5  =  C6H6.CO.OC2H6  +  H2O  +  N2. 

If  its  solution  in  aqueous  ether  be  treated  with  sodium 
amalgam  and  kept  neutral  by  the  addition  of  hydrochloric 
acid,  benzyl  alcohol  is  formed.8 

1  Gorhardt,  Chim.  Org.  iii.  268. 

2  Keknle,  Bcr.  Deutsch.  Chem.  Ges.  vi.  113. 

3  Klein,  Ann.  Chem.  Pharm.  clxvi.   184. 

4  Schiff  and  Tassinari,  Ber.  Deutsch.  Chem.  Ges.  x.  1785. 

5  Wohler,  Ann.  Chem.  Pharm.  cxcii.  362. 

6  Guareschi,  ibid,  clxxi.  141. 

7  Meyer  and  Stiiber,  ibid  clxv.  186. 

8  Guareschi,  Bcr.  Deutsch,  Chem.  Ges.  vii.  1462. 


174  AROMATIC  COMPOUNDS. 

It  is  converted  into  aniline  by  the  action  of  bromine  in 
alkaline  solution,  just  as  acetamide  in  similar  circumstances 
yields  methylamine  (p.  113). 

Benzamide  hydrochloride,  C6H5.CO.NH2.C1H,  is  formed  by 
dissolving  benzamide  in  hot  concentrated  hydrochloric  acid,1 
or  by  passing  hydrochloric  acid  into  a  mixture  of  equal  mole- 
cules of  benzonitril  and  water.2  It  crystallizes  in  long  prisms, 
which  rapidly  lose  acid  in  the  air. 

Mercuric  lenzamide,  (C6H5.CO.NH)2Hg,  is  prepared  by  dis- 
solving mercuric  oxide  in  a  hot,  aqueous  solution  of  benzamide ; 3 
on  cooling  the  liquid,  a  semi-solid  crystalline  mass  is  formed, 
which  is  obtained  by  re-crystallization  from  alcohol  in  plates 
melting  at  222°— 224°.* 

2105  Benzoyl  derivatives  of  amines  and  amido-bases  are  formed 
by  the  action  of  benzoyl  chloride  on  the  latter : 

Melting-  Boiling- 

point,  point. 

Dimethylbenzamide  : 5 

C6H5.CO.N(CH3)2,  large  crystals  .  41°— 42°         255°— 257° 

Diethylbenzamide  : 6 

C6H5.CO.N(C2H5)2,  liquid  .    ...  280°— 282° 

Ethylenebenzamide : 7 

(C6H5.CO.NH)2C2H4,  needles    .    .      249° 

Benzanilide,  or  Benzoylaniline,  C6H5.N(CO.C6H5)H.  Gerhardt 
obtained  this  compound  by  the  action  of  benzoyl  chloride  on 
aniline,8  and  Leuckart  found  that  it  is  also  formed  when  phenyl 
isocyanate  is  treated  with  benzene  in  presence  of  aluminium 
chloride.9  It  is  insoluble  in  water  and  crystallizes  from  alcohol 
in  nacreous  plates,  which  melt  at  160° — 161  °,10  and  volatilize 
without  decomposition  at  a  higher  temperature.  It  is  not 
attacked  by  boiling  aqueous  acids  or  alkalis,  but  yields  aniline 
and  benzoic  acid  when  it  is  fused  with  caustic  potash.  Concen- 


1  Dessaignes,  Ann.  Chem.  Pharm.  Ixxxii.  234. 

-  Pinner  and  Klein,  Ber.  Deutsch.  Chem.  Gcs.  x.  1896  ;  xi.  10. 
3  Dessaignes,  loc.  tit. 

*  Oppenheim,  Bcr.  Deutsch.  Chem.  Gcs.  vi.  1392, 

5  Hallmann,  ibid.  ix.  846. 

6  Ibid. 

7  Hofmann,  ibid.  v.  246  ;  Kraut  and  Schwartz,  Ann.  Chem.  Pharm.  ccxxiii.  43. 

8  Ibid.  Ix.  311  ;  Ixxxvii.  164. 

9  Bcr.  Deutsch.  Chem.  Gcs.  xviii.  873. 

10  Wallach  and  Hofmann,  Ann.  Chem.  Pharm.  clxxxiv.  80. 


BENZANILIDE.  175 


trated  nitric  acid  converts  it  into   the   three  isomeric  lenzoyl- 
nitmnilines,  C6H4(N02)N(CO.C6H5)H  : 

Melting-point. 
Ortho,1  long,  light  yellow  needles  .    .  94°— 95° 

Meta,2    plates 155'5° 

Para,3    small  prisms   .......  199° 


The  two  latter  are  converted  by  reduction  into  the  corre- 
sponding benzoyldiamidobenzenes,  C6H4(NH2)N(OO.C6H5)H, 
while  the  ortho-compound  forms  phenylenebenzamidine, 

XNH\ 
C6H5.C-,v          yC6H4,  a  substance  which  will  be  subsequently 

^  N  ' 
described. 

Melting  point. 
Benzoylmethylaniline  : 5 

C6HftN(CO.C6H5)CH3,  small  monoclinic  crystals       59° 

Benzoyldiphenylamine : 6 

(C6H5)2N(CO-C'6H5),  rhombic  needles     .    .    .  176°— 177° 

Benzoylorthotoluide : 7 

(C6H4.CH3)N(CO.C6H5)H,  needles     ....  142°— 143° 

Benzoylparatoluide  : 8 

(C6H4.CH3)N(CO.C6H5)H,  long  needles      .    .       155° 

2106  Methylenedibenzamide,CK2(N~H..CQ.CQR5)2.  By  heating 
hippuric  acid,  C9H9N03  (p.  181),  with  lead  peroxide  and  dilute 
sulphuric  or  nitric  acid,  Schwarz  obtained  a  crystalline  substance, 
which  he  extracted  from  the  product  by  alcohol.  This  dissolves 
in  concentrated  sulphuric  or  nitric  acid  without  change,  and  is 
only  attacked  by  oxidizing  agents  with  difficulty  and  he  therefore 
called  it  hipparaffin  (ITTTTO?,  parum  affinis).  Its  analysis  led  to 
the  formula  C16H16N2O2.9  Maier,  who  also  prepared  it,  assigned 
to  it  the  composition  C8H7NO,  and  found  that  another  crystal- 
line substance,  hipparin,  C8H9NO2,  is  obtained  in  its  prepara- 
tion.10 Schwarz  subsequently  resumed  his  investigation,  and 
showed  that  the  latter  compound  is  ethyl  hippurate  ;  by  heating 

1  Mears,  Bcr.  Dcutsch.  Chem.  Ges.  ix.  774  ;  Schwarz,  ibid.  x.  1709. 

2  Bell,  ibid.  vii.  498  ;  Hiibner,  ibid.  x.  1716. 

3  Stover,  ibid.  vii.  463  and  1314. 

4  C.  A.  Bell,  ibid.  vii.  497  arid  1504  ;  Sennewald,  ibid.  ix.  775  ;  Stover,  loe.  cit. 
Hepp,  ibid.  x.  237. 

6  Hofmann,  Ann.  Chem.  Pharm.  cxxxii.  166  ;  Bernthsen,  ibid,  cxcii.  13. 

7  Bruckner,  ibid.  ccv.  230. 

8  Kelbe,  Bcr.  Dcutsch.  Chem.  Gcs.  viii.  875. 

9  Ann.  Chem.  Pharm.  Ixxv.  201. 
10  Ibid,  cxxvii.  162. 


176  AROMATIC  COMPOUNDS. 

hipparaffin  with  water  to  170° — 180°,  he  obtained  benzamide 
and  a  substance  which  gave  the  reactions  of  an  aldehyde,  and 
which  he  identified,  in  spite  of  some  differences  in  its  properties, 
with  the  ethylenedibenzimide  which  he  had  obtained  by  the 
action  of  phosphorus  pentoxide  on  a  mixture  of  aldehyde  and 
benzamide.1  Kraut  and  Schwarz,  however,  found  that  it  is 
actually  identical  with  methylenedibenzamide,2  which  had  been 
obtained  by  Hepp  and  Spiess  by  the  action  of  concentrated 
sulphuric  acid  on  a  mixture  of  methylal,  CH2(OCH3)2,  and 
benzonitril.3 

It  is  insoluble  in  cold,  slightly  soluble  in  hot  water,  and 
crystallizes  from  alcohol  in  bushy  aggregates  of  needles,  melting 
at  223°.  It  is  decomposed  on  boiling  with  32  per  cent,  sulphuric 
acid,  with  formation  of  ammonia,  benzoic  acid  and  formaldehyde. 

Ethidenedibenzamide,  CH3.CH(NH.COC6H5)2.  Limpricht 
obtained  this  compound  by  the  action  of  benzoyl  chloride  on 
aldehyde-ammonia,4  and  Nencki  by  that  of  benzamide  on  alde- 
hyde containing  a  few  drops  of  hydrochloric  acid.5  It  is  prepared 
by  adding  first  paraldehyde  and  then  benzonitril  to  well-cooled 
sulphuric  acid,  and  diluting  with  water  after  some  hours  (Hepp 
and  Spiess).  It  crystallizes  from  alcohol  in  long,  white  needles, 
which  melt  at  204°  and  sublime  without  decomposition.  It  is 
decomposed  by  fuming  nitric  acid  into  aldehyde  and  benzamide. 

Dibenzamide,  N(CO.C6H5)2H,  was  prepared  by  Baumert  and 
Landolt,  together  with  benzamide,  by  the  action  of  benzoyl 
chloride  on  potassium  amide.6  Barth  and  Senhofer  found  that 
it  is  readily  formed  when  benzonitril  is  treated  with  a  mixture 
of  sulphuric  acid  and  phosphorus  pentoxide ;  the  solution  is 
allowed  to  stand  for  some  hours  and  then  diluted  with  water, 
which  slowly  precipitates  the  compound  in  crystals : 7 

2C6H5.CN  +  2H20  =  (C6H5.CO)2NH  +  NH3. 

It  is  also  formed  when  lophine,  which  is  obtained  by  the 
dry  distillation  of  hydrobenzamide,  is  treated  with  a  solution 
of  chromium  trioxide  in  acetic  acid,  it  being  thus  smoothly 
converted  into  benzamide  and  dibenzamide  :  8 

C21H16N2 + 20  +  H20  =  C7H5O.NH2 + (C7H5O)2NH. 

1    Wicn.  Akad.  Ber.  Ixxvii.  762.  2  Ann.  Chtm.  Pharm.  ccxxiii.  40. 

3  Ber.  Dcutsch.  Chem.  Ges.  ix.  1424.  4  Ann.  Chcm.  Pharm.  xcix.  119. 

6  Ber.  Dcutsch.  Chem.  Ges.  vii.  159.  6  Ann.  Chem.  Pharm.  exi.  5. 

7  Ber.  Dcutsch.  Chem.  Ges.  ix.  975,  1073.  8  E.  Fischer  and  Proschke,    ibid. 

xiii.  708. 


THIOBENZAMIDE. 

separates  from  dilute  alcohol  in  long,  thin  needles,  which 
It  at  148°,  and  decompose  at  a  higher  temperature,  giving  ofi 
odour  of  benzaldehyde.  It  is  almost  insoluble  in  cold  and 
:ely  soluble  in  hot  water,  but  dissolves  readily  in  ether, 
chloroform  and  benzene,  from  the  last  two  of  which  it  separates 
in  rhombic  crystals.  On  boiling  with  caustic  potash  it  decom- 
poses into  benzoic  acid  and  ammonia. 

It  dissolves  readily  in  dilute  caustic  soda,  the  solution  when 
centrated  depositing  small  glittering  needles  of  the  com- 
pound (C7H5O)2NNa ;  it  also  occurs  in  short,  distorted  prisms 
containing  half  a  molecule  of  water,  which  is  lost  at  120°. 
The  solution  gives  a  precipitate  with  silver  nitrate,  consisting 
of  (C7H5O)2NAg,  and  is  also  precipitated  by  other  metallic  salts. 

Schafer,  by  heating  benzamide  in  a  stream  of  hydrochloric 
acid,  obtained  a  compound  which  he  considered  to  be  dibenz- 
amide  hydrate  (C7H50)2NH  +  2H20;  it  crystallizes  in  small 
plates,  which  melt  at  99°,  and  do  not  lose  water  at  a  higher 
temperature,  but  decompose  into  benzoic  acid  and  benz- 
amide.1 This  substance  is  evidently  acid  ammonium  benzoate, 

C7H5(NH4)0.2+C7H602.2 

Dibenzanilide,  (C6H5.CO)?NC6H5.  Gerhardt  and  Chiozza  ob- 
tained this  compound  by  the  action  of  benzoyl  chloride  on  benz- 
anilide.  It  crystallizes  from  alcohol  in  fine,  lustrous  needles, 
which  melt  at  137°  and  sublime  when  more  strongly  heated.3 
By  heating  benzoic  acid  with  phenyl  mustard  oil,  Losanitsch 
obtained  a  crystalline,  foliaceous  mass  of  a  dibenzanilide,  melt- 
ing at  1550.4  Steiner,  on  the  other  hand,  who  prepared  it  by 
Gerhardt's  method  and  also  by  heating  tribenzhydroxylamine, 
N(OC7H50)(C7H5O)2,  found  the  melting-point  of  both  prepara- 
tions to  be  1610.5 

Thiobenzamide,  C6H5.CS.NH2,  was  prepared  by  Cahours  by 
passing  sulphuretted  hydrogen  into  an  alcoholic,  ammoniacal 
solution  of  benzonitril : 

C6H5.CN  +  SH2  =  C6H5.CS.NH2. 

It  crystallizes  from  hot  water  in  long,  yellow  needles,  melting 
at  117° ;  when  heated  with  water  and  mercuric  oxide,  it  is  recon- 
verted into  benzonitril,  while  it  is  reduced  to  benzylamine  by 

1  Ann.  Chem.  Pharm.  clxix.  111. 

2  Beilstein,  Org.  Chem.  1101. 

8  Ann.  Chcm.  Pharm.  Ixxxvii.  302. 

4  Bcr.  Deutftch.  Chem.  Gcs.  vi.  176. 

5  Ann.  Chcm.  Pharm.  clxxviii.  235. 


178  AROMATIC  COMPOUNDS. 

zinc  and  hydrochloric   acid.1      Iodine  acts   upon    its    alcoholic 
solution  in  the  following  manner : 

2C7H7SN  +  2I2  =  CUH10SN2 + 4HI  +  S. 

The  compound  obtained  in  this  way  crystallizes  from  hot 
alcohol  in  lustrous,  snow-white  needles,  which  melt  at  90°  and 
distil  without  decomposition  at  a  higher  temperature.  It  is  a 
very  stable  compound,  and  is  not  altered  by  being  heated  to  150° 
with  hydrochloric  acid,  sulphuric  acid  or  tolerably  concentrated 
nitric  acid.  On  boiling  with  caustic  potash  it  is  gradually  con- 
verted into  benzoic  acid,  ammonia  being  evolved.  Zinc  and 
hydrochloric  acid  reduce  it  in  alcoholic  solution  to  the  base, 
CUHMN2,2  which  is  isomeric  with  ethenyldiphenylamidine 
(Part  III.  p.  217)  ;  benzene  and  benzonitril  are  simultaneously 
formed.3  It  crystallizes  in  small  plates,  melting  at  71°,  is  a 
monacid  base  and  forms  an  alkaline  solution  in  alcohol. 

Thiolenzanilide,  or  Phenylthiobenzamide,  C6H5.CS.N(C6H5)H, 
is  formed  when  benzanilide  is  heated  with  phosphorus  penta- 
sulphide,4  and  crystallizes  from  alcohol  in  thin,  yellow  tablets  or 
prisms,  melting  at  97*5° — 98'5°. 

DiphenyltMobenzamide,  C6H5.CS.N(C6H5)2,  is  formed  when 
asymmetric  diphenylbenzenylamidine  is  heated  to  130° — 140° 
with  carbon  disulphide  : 

C6H5.C(NH)N(C6H6)2  +  CS2= C6H5.CS.N(C6H5)2  +  CNSH. 

It   crystallizes   from   solution   in   benzene  or   alcohol   in   dark 
yellow,  asymmetric  prisms,  melting  at  150° — 1510.5 

2107  Benzoyl  urea,  C6H5.CO.NH.CO.NH2.  Zinin  obtained 
this  compound  by  heating  urea  to  150° — 155°  with  benzoyl 
chloride ; 6  the  anhydride  may  be  substituted  for  the  chloride  in 
this  reaction.7  The  monobenzoyl  urea  crystallizes, from  alcohol  in 
long,  thin  plates,  which  melt  at  about  200°  and  decompose  into  benz- 
amide  and  cyanuric  acid  when  carefully  heated  beyond  this  point. 


{N  H  \ 
NH  GO  0  H  '  neec^es- 

Asymmetric  ethyl- )   /-,/-i    f  NH9  ,       i    -,     •, 

QJ      >  OC   <  TVT//~<  TT  \nr\  ri  TT  ,  rhombonedra. 
benzoyl  urea,9      J  \  N(C2H5)CO.C6H5' 


1  Hofmann,  Ber.  Deutsch.  Chem.  Ges.  i.  102.  2  Ibid.  ii.  644. 

3  Wanstrat,  ibid.  vi.  335.  4  Bernthsen,  ibid.  xi.  503. 

5  Bernthsen,  Ann.  Chem.  Pharm.  .cxcii.  37.  6  Ibid.  xcii.  404. 

7  Geuther,  Scheitz  and  Marsh,  Zeitschr.  Chrm.  1868,  305. 

8  Leuckart,  Journ.  Prakt.  Chem.  [2]  xxi.  33  ;  Miquel,  Ann.   Chim.  Phys.  [5] 
xi.  318.  9  Lossner,  Journ.  Prakt.  Chem.  [2]  x.  251. 


DIBENZOYL  UREA. 


Dibenzoyl  urea,  CO(NH.CO.C6H5)2,  is  formed,  together  with 
ijdrochloric  acid,  carbon  dioxide,  ammonium  chloride,  benzoic 
;id  and  benzonitril,  when  benzamide  is  heated  to  160° — 170° 
carbonyl  chloride,1  and  also  from  guanidine  and  benzoic 
lydrideat  100°  :2 


C=NH2 


=NH  +  0< 


,CO.C6H5 


NH.CO.C6H5 


=  NH,+CO 


NI 


NH.CO.C6H5. 


It  crystallizes  from  alcohol  in  needles  melting  at  210°,  and  is 
decomposed  by  boiling  with  strong  acids  into  carbon  dioxide, 
ammonia  and  benzoic  acid,  while  dilute  caustic  potash  solution 
converts  it  into  benzamide  and  carbon  dioxide. 

Benzoyl  thio-urea,  C6H5.CO.NH.CS.NH2,  is  formed  when  thio- 
urea  is  heated  with  benzoyl  chloride  3  and  by  the  action  of  dilute 
ammonia  on  benzoyl  thiocyanate.4  It  crystallizes  from  dilute 
alcohol  in  small  prisms  which  have  a  very  bitter  taste  and  melt 
at  171°. 

Miquel  has  prepared  the  following  compounds  by  the  action 
of  benzoyl  thiocyanate  on  amines  and  amido-bases  : 


Ethylbenzoyl  thio-urea  : 


, 

&  needles. 


'henylbenzoyl  thio-urea : 
/  NH.CO.C6H5 
1  NH.C6H5       ' 
>enzylbenzoyl  thio-urea  : 
NH.CO.C6H, 

NH.CH2.C6H5'  sma11  Pnsms' 
Paratolylbenzoyl  thio-urea : 
NH.CO.C6H5 


Melting-point. 

134° 

.       148°— 149° 
145° 
165° 


Benzoylphenylhydrazine,  C6H5.NH  -  NH(CO.C6H5).  In  order 
to  obtain  this  compound,  two  molecules  of  phenylhydrazine  are 
dissolved  in  five  times  their  amount  of  ether,  the  solution  cooled 


1  Schmidt,  Journ.  PrakL  Chem.  [2]  v.  58. 

2  Creath,  Ber.  Dcutsch.  Chem.  Ges.  vii.  1739. 

3  Pike,  ibid.  vi.  755. 

4  Miquel,  Ann.  Chim.  Phijs.  [5]  xi.  313. 


AROMATIC  COMPOUNDS. 


and  then  treated  with  a  molecule  of  benzoyl  chloride.  The 
mixture  is  filtered,  the  hydrochloride  of  phenylhydrazine  removed 
by  boiling  with  water,  and  the  residual  benzoylphenylhydrazine 
crystallized  from  boiling  alcohol.  It  forms  fine  prisms,  melting 
at  168°,  dissolves  readily  in  warm,  dilute  caustic  potash,  and 
is  precipitated  from  this  solution  by  acids.  Yellow  mercuric 
oxide  converts  it  in  alcoholic  solution  into  benzoylazobenzene, 
C6H5.N=N.CO.C6H5,  a  dark  red,  oily  liquid,  which  is  reconverted 
into  the  original  compound  by  reduction.1 

Methylbenzoylphenylhydrazine,  C6H5N(CH3).NH(CO.C6H5). 
This  compound  is  prepared  by  adding  sodium  and  then  methyl 
iodide  to  a  solution  of  benzoylhydrazine  in  wood-spirit;  the 
mixture  becomes  warm,  and  after  standing  for  several  hours  is 
heated  to  100°  for  a  short  time  in  order  to  complete  the  reaction. 
Methylbenzoylphenylhydrazine  crystallizes  from  hot  alcohol  in 
fine,  white  needles,  melting  at  153°.  When  its  solution  in 
hydrochloric  acid  is  treated  with  a  trace  of  nitrous  acid,  an 
intense  red  colouration  is  produced,  which  becomes  dark  brown 
with  large  quantities.  When  methylbenzoylphenylhydrazine  is 
heated  with  concentrated  hydrochloric  acid,  it  is  decomposed  into 
benzoic  acid  and  methylphenylhydrazine  ;  the  latter  compound 
may  be  detected  by  conversion  into  its  characteristic  tetrazone, 
which  melts  at  137°,  and  not,  as  was  formerly  stated,  at  133° 
(Part  III.  p.  270).2 

Dibenzoylphenylhydrazine,  C6H5N(CO.C6H5)N(CO.C6H5)H,  is 
obtained  by  the  action  of  benzoyl  chloride  on  benzoylphenyl- 
hydrazine or  on  potassium  phenylhydrazinesulphonate.  It  crystal- 
lizes from  hot  alcohol  in  fine  prisms,  which  melt  at  177°  —  178°, 
and  dissolve  slowly  in  aqueous  alkalis.  If  the  alkaline  solution 
be  treated  with  the  calculated  quantity  of  sodium  and  heated,  the 
sodium  dissolves  and  on  cooling,  a  salt,  C20H15N2O2Na,  separates 
out  in  lustrous  plates,  which  are  readily  soluble  in  water. 

M^hj^ibm^lph^ 

CH3,  is  formed  when  the  solution  of  the  sodium  salt  is  heated 
with  methyl  iodide.  It  forms  well-developed,  soft,  white  crystals 
which  melt  at  145°,  and  are  insoluble  in  water  or  alkalis,  but 
dissolve  readily  in  hot  alcohol.  On  distillation  with  caustic 
potash  it  is  decomposed  into  benzoic  acid  and  hydrazophenyl- 
mcthyl,  C6H5.NH  —  NH(CH3).  This  substance  is  a  colourless  oil 
which  rapidly  oxidizes  in  the  air,  but  forms  stable  salts.  When 

1  E.  Fischer,  Ann.  Chcm.  Pharni.  cxc.  125. 
3  Tafel,  Ber.  Dcutsch.  Chem.  Ges.  xviii.  1739. 


HIPPUR1C  ACID.  181 


mercuric  oxide  is  added  to  its  ethereal  solution,  it  is  converted 
into  azophenylmethyl,  C^NizzNCHg,  a  yellow  oil,  which  pos- 
sesses a  characteristic  smell,  volatilizes  with  ether  vapour,  more 
rapidly  with  steam,  and  distils  at  about  150°  with  considerable 
decomposition  (Tafel). 

Benzoyldiphenylhydrazine^CfiH.^^!  —  NH(CO.C6H5),  was  ob- 
tained by  Fischer  from  benzoyl  chloride  and  diphenylhydrazine ; 
it  is  slightly  soluble  in  alcohol  and  ether,  and  crystallizes  from 
hot  acetone  in  fine  needles,  melting  at  1920.1 


HIPPURIC  ACID,  C9H9NO3. 

2108  Rouelle,  in  the  year  1776,  as  has  been  already  mentioned 
under  benzoic  acid,  found  a  salt  in  the  urine  of  the  cow  and  the 
camel,  which  is  analogous  to  flowers  of  benzoin,  and  Fourcroy 
and  Vauquelin  observed  a  peculiar  acid,  which  they  took  to  be 
benzoic  acid,  in  the  urine  of  graminivora.  Liebig,  however, 
showed  in  1829,  that  this  acid  contains  nitrogen  and  differs 
completely  from  benzoic  acid  in  its  properties  ;  he  says,  '  Since 
I  have  more  especially  investigated  the  acid  obtained  from  the 
urine  of  the  horse,  I  will  designate  it,  for  want  of  a  more  suit- 
able term,  as  "  hippuric  acid  "  (tWo?,  horse,  ovpov,  urine).  On 
heating  it  decomposes  with  formation  of  various  products,  among 
them  being  benzoic  acid,  the  experience  of  Fourcroy  and 
Vauquelin,  "  that  benzoic  acid  can  be  obtained  from  horse's 
urine,  but  is  not  contained  in  it  as  such  "  being  thus  confirmed/  2 
Liebig  first  obtained  for  it  the  formula  C10H10NO3,  which  he 
subsequently  corrected,3  his  later  analyses  being  confirmed  by 
those  of  Dumas  and  Peligot.4  Pelouze  then  found  that  on 
boiling  hippuric  acid  with  manganese  dioxide  and  very  dilute 
sulphuric  acid,  benzoic  acid,  ammonia  and  carbon  dioxide  are 
formed,5  while  Fehling  obtained  benzamide  and  carbon  dioxide 
by  boiling  it  with  water  arid  lead  dioxide.6  Dessaignes  then  made 
the  important  observation  that  it  is  decomposed  into  .benzoic 
acid  and  glycocoll  (amido-acetic  acid)  when  treated  with  boiling 
alkalis  or  acids,7  and  he,  with  the  majority  of  chemists, 

1  Ann.  Chcm.  Pharm.  cxc.  78.  2  Pogg.  Ann.  xvii.  389. 

3  Ibid,  xxxii.  573.  4  Ann.  Chcm.  Pharm.  xiv.  69. 

6  Ibid,  xx vi.  60.  6  Ibid,  xxviii.  40. 

7  Journ.  Prald.  Chcm.  xxxvii.  244. 

243 


182  AROMATIC   COMPOUNDS. 

assumed  that  hippuric  acid  is  a  copulated  compound  of  benzoic 
acid  and  glycocoll,  although,  as  was  pointed  out  by  Berzelius, 
this  assumption  does  not  in  the  least  account  for  the  action  of 
lead  dioxide. 

An  important  advance  towards  the  determination  of  the  consti- 
tution of  hippuric  acid  was  made  by  Strecker,1  who  found  that  it  is 
converted  by  the  action  of  nitrous  acid  into  benzoylglycollic  acid 
(p.  165),  which  was  more  closely  investigated  by  him  in  conjunc- 
tion with  Sokolow.  This  compound  assumes  the  elements  of 
water  and  splits  up  into  benzoic  acid  and  glycollic  acid,  and  must, 
therefore,  be  considered  as  a  copulated  compound  of  these,  its 
amido-derivative  being  hippuric  acid.2 

Dessaignes  now  endeavoured  to  prepare  hippuric  acid  arti- 
ficially by  heating  glycocoll  with  benzoyl  chloride,  but  without 
success ;  he  attributed  his  failure  to  the  evolution  of  hydrochloric 
acid  and  therefore  substituted  the  zinc  salt  of  glycocoll,  zinc 
amido- acetate,  and  found  that  hippuric  acid  is  slowly  formed 
when  benzoyl  chloride  is  allowed  to  act  upon  this  in  the  cold, 
more  rapidly  at  1200.3  He  also  obtained  it  subsequently  by  heat- 
ing benzoic  acid  with  glycocoll  to  1600,4  and  Jazukowitzsch  pre- 
pared it  by  heating  chloracetic  acid  with  benzamide ;  5  the  yield 
was,  however,  small,  owing  to  the  formation  of  free  hydrochloric 
acid.  These  syntheses  finally  proved  that  hippuric  acid  is 
benzoylamido-acetic  acid  : 

CH2.NH2  CH2.NH.CO.C6H5 

+  HO.CO.C6H5  =  |  +H20. 

COOH  CO.OH 

CH,C1  CH2.NH.CO.C6H5 

|  +NH2CO.C6H6=  |  +  HC1. 

CO.OH  CO.OH 

It  is  also  formed,  together  with  other  products  which  will  be 
subsequently  mentioned,  from  benzoyl  chloride  and  silver  amido- 
^acetate,6  and  very  readily  when  glycocoll  is  heated  with  benzoic 
anhydride  7  or  when  benzoyl  chloride  is  added  to  a  concentrated 
aqueous  solution  of  the  former.8 

Liebig  detected  it  in  human  urine,  about  1  grm.  being  excreted 

1  Ann.  Chcm.  Pkarm.  Ixviii.  54.  2  Ibid.  Ixxx.  17. 

3  Ibid.  Ixxxvii.  325.  *  Jahresber.  Ohem.  1857,  367. 

6  Zeitschr.  Chcm.  1867,  466. 

6  Journ.  PraJct.  Chem.  [2]  xxiv.  239  ;  xxvi.  145. 

7  Curtius,  Be,r.  Deutsch.  Chcm.  Ges.  xvii.  1662. 

8  Baum,  Zeitschr.  Physiolog.  Chem.  ix.  465. 


HIPPURIC  ACID.  ]83 


per  diem.1  According  to  Weismann  it  is  formed  more  freely  during 
a  vegetable  than  an  animal  diet,2  and  according  to  Ducheck 
it  is  not  invariably  present.3  Pettenkofer  found  1'3  per  cent,  of 
it  in  the  urine  of  a  girl  suffering  from  St.  Vitus's  dance,  whose 
diet  consisted  exclusively  of  apples  and  bread ;  the  amount 
decreased  as  soon  as  meat  was  again  taken.4 

Lehmann  observed  its  occurrence  during  diabetes,  even  before 
Liebig  had  detected  its  presence  in  normal  human  urine,5  and 
since  that  time  it  has  frequently  been  observed  in  large 
quantities  in  diabetic  urine.  It  also  occurs  largely  in  the  acid 
urine  of  persons  suffering  from  fevers  of  every  kind.6 

Liebig,7  and  Dumas  8  assumed  that  fresh  horses'  urine  contains 
hippuric  acid  which  is  converted  into  benzoic  acid  on  standing. 
The  former  subsequently  stated  that  horses  and  bullocks  excrete 
hippuric  aciol  when  they  are  allowed  to  remain  idle  for  some 
time,  and  benzoic  acid  when  they  are  working  to  the  full  extent 
of  their  powers,9  and  Erdmann  and  Marchand  found 10  that  the 
urine  of  carriage  horses  usually  contains  the  former  and  that  of 
plough  horses  the  latter.  Lehmann,  however,  who  investigated 
the  urine  of  a  large  number  of  horses,  both  sound  and  diseased, 
well  and  badly  fed,  found  only  hippuric  acid  without  exception, 
provided  that  the  urine  had  not  been  allowed  to  stand  too  long 
in  the  air.  After  standing  for  a  considerable  time,  and  especially 
after  the  formation  of  ammonia,  only  benzoic  acid  is  present, 
being  formed  by  a  special  ferment.  When  such  urine  was  added 
to  a  sample  of  the  fresh  material,  containing  hippuric  acid  alone, 
the  latter  decomposed  on  evaporation  and  only  benzoic  acid  could 
then  be  detected.11  Roussin  found  a  large  quantity  of  urea  but 
no  hippuric  acid  in  the  urine  of  Arab  stallions,  which  did  not 
work  but  were  kept  for  breeding  ;  that  of  others,  which  were  used 
by  the  Spahis  for  riding,  contained  little  urea,  but  0'5 — 1  per 
cent,  of  hippuric  acid  ;  in  one  sample  of  urine  which  was  passed 
after  a  long  journey  the  amount  rose  to  1*4  per  cent.,  and  0'78 
per  cent,  was  found  in  that  of  omnibus  horses.12 

Stiideler  found  about  1*5  per  cent,  of  hippuric  acid  in  cows' 

1  Baum,  Zcitschr.  Physiolog.  Chein.  cvi.  164. 

2  Jahresber.  Chcm.  1858,  572.  3  Gmelin,  Org,  Chem.  v.  332.        , 
4  Ann.  Chem.  Fharm.  Hi.  86.  5  Journ.  Prdkt.  Chem.  vi.  113. 

6  Gmelin's  Org.  Chem.  v.  334.  7  Ann.  Chem.  Pharm.  xxx.  280. 

8  Ann.  Chim.  Phys.  Ivii.  331. 

*  Ann.  Chem.  Pharm.  xli.  272  ;  Organ.  Chem.  in  Anwendung  auf  Phys. 
und  Pathol.  Ixxxiv. 

10  Journ.  PraJct.  Chem.  xxvi.  491.  u  Gmelin,  Organ.  Chem.  v.  332. 

12  Compt.  rend.  xlii.  583. 


184  AROMATIC  COMPOUNDS. 

urine,1  and,  according  to  Hallwachs,  a  cow  passes  more  than 
50  grms.  of  the  acid  during  twenty-four  hours.2  Kraut  observed 
that  cows  which  are  allowed  to  graze  give  more  hippuric  acid 
than  those  which  are  stall  fed,3  while  only  traces  are  formed 
when  they  are  fed  on  spent  grain  from  a  distillery.4 

In  the  urine  of  cows  fed  on  oat-straw  and  wheat-straw,  with 
the  addition  of  some  beans,  2'1 — 2*7  per  cent,  was  found,  while 
that  of  cattle  fed  on  bean-straw  and  clover  contained  only  0'4  ]>LT 
cent.,  and  when  ordinary  meadow  hay  was  given,  1*4  per  cent.5 
The  urine  of  sucking  calves  contains  uric  acid  but  no  hippuric 
acid  (Wohler).  The  latter  occurs  in  the  urine  of  sheep,  goats, 
hares,  rabbits,  and  elephants  (Schwarz).  Schwarz  found  it  in 
very  considerable  quantity  in  the  urine  of  a  camel,  the  sample 
being  very  concentrated,  as  only  four  ounces  were  passed  during 
the  day,  and  Lehmann  detected  it  in  the  urine  of  the  tortoise 
(Testudo  graeca).  Pettenkofer  observed  its  occurrence  in  the 
scurf  which  is  formed  on  the  skin  during  the  rare  disease  known 
as  ichthiosis,6  and  J.  Davy  found  it  in  butterflies,  moths,  and 
their  chrysalides  and  excrements.7 

The  urine  of  dogs  also  contains  a  small  quantity  of  the  acid 
even  during  an  exclusively  meat  diet  or  after  long  fasting,8 
while  it  has  never  been  found  in  the  urine  of  pigs.9 

2109  Ure  was  the  first  to  make  the  important  observation 
that  the  urine  of  a  patient  who  has  taken  benzoic  acid  contains 
a  large  amount  of  hippuric  acid.10  Wohler  had  previously 
suggested  that  benzoic  acid  is  changed  to  hippuric  acid  in  the 
organism,  for  he  had  found  in  the  urine  of  a  dog  to  which  half  a 
drachm  of  benzoic  acid  had  been  given  an  acid  which  he  mistook 
for  benzoic  acid,  but  which  he  subsequently  found  to  be  identical 
with  the  hippuric  acid  discovered  by  Liebig.11  Under  his  direc- 
tions Keller  conducted  a  research  on  the  subject,  taking  2  grains 
of  benzoic  acid  in  the  evening  and  repeating  the  dose  three  times 
daily  during  the  following  days.  His  urine,  which  now  possessed 
a  strongly  acid  reaction,  contained  a  considerable  amount  of 
hippuric  acid,  and,  as  Wohler  says,  "  since  benzoic  acid  seems 

1  Ann.  Chem.  Pharm.  Ixxvii.  17.  2  Ibid.  cv.  209 

3  Chem.  Centralbl.  1858,  831. 

4  Schwarz,  Ann.  Chem.  Pharm.  liv.  31. 

6  Henneberg,  Stohmann  and  Rautenberg,  ibid,  cxxiv.  201.          6  Ibid.  xc.  378. 

7  New  Edinb.  Phil  Journ.  xlv.  17. 

8  Salkowski,  Ber.  Deutsch.  Chem.  Ges.  xi.  500. 

9  Boussingault,  Ann.  Chim.  Phys.  [3]  xv.  97  ;  von  Bibra,  Ann.  Chem.  Pharm. 
liii.  98. 

10  Repert.  Pharm.  xxvii.  642. 

11  Berzelius,  Lehrb.  Chem.  1831,  iv.  376. 


HIPPURIC  ACID.  185 


not  to  affect  the  health,  large  quantities  of  hippuric  acid  might 
readily  be  prepared  in  this  manner,  the  only  requisite  being  a 
man  who  would  continue  the  manufacture  for  weeks.1  These 
observations  were  confirmed  by  Garrod,2  Schwarz  and  others; 
Marchand  found  39  2  grains  of  hippuric  acid  in  his  urine  after 
eating  30  grains  of  benzoic  acid.3 

Many  other  compounds,  which  are  converted  into  benzoic  acid 
by  oxidation,  are  changed  into  hippuric  acid  by  their  passage 
through  the  organism  ;  such  are  benzaldehyde,4  cinnamic 
acid,5  C6H5.CH=CH.CO2H,  hydrocinnamic  acid  or  phenylpro- 
pionic  acid,6  C6H5.C2H4.CO2H,  phenylglycollic  acid,7  C6H5.CH 
(OH)CO2H,  quinic  acid,8  C6H7(OH)4CO2H,  and  even  toluene.9 
The  substitution  products  of  benzoic  acid  appear  in  the  urine  as 
the  corresponding  derivatives  of  hippuric  acid  ;  thus  phenylacetic 
acid,  C6H5.CH2.CO2H,  gives  phenylaceturic  acid10;  salicylic  acid, 
C6H4(OH)C02H,  is  converted  into  salicyluric  acid,11  and  toluic 
acid,  C6H4(CH3)C02H,  into  toluyluric  acid;12  phthalic  acid, 
however,  remains  unchanged.13  It  follows  from  this,  that  the 
monobasic  aromatic  acids,  and  hydroxy-acids,  combine  with 
glycocoll  with  elimination  of  water  in  their  passage  through  the 
organism. 

After  Liebig  had  discovered  hippuric  acid,  he  raised  the  ques- 
tion whether  it  must  be  considered  as  a  compound  of  benzoic 
acid  with  an  unknown  compound  body,  or  as  a  peculiar  acid  by 
the  decomposition  of  which  benzoic  acid  is  formed,  just  as  oxalic 
and  formic  acids  are  formed  when  sugar  or  starch  is  treated  with 
nitric  acid.  He  decided  for  the  latter  view,  and  says:  "The 
first  view  is  rendered  improbable  by  the  fact  that  I  have  been 
unable  to  prepare  even  the  slightest  trace  of  benzoic  acid  from 
horses'  fodder,  which  is  the  source  of  their  urine,  even  if  this 
acid  be  contained  in  Anthoxanthum  odoratum  and  Holcus  odoratus, 
as  found  by  Vogel,  its  identity  being  rendered  doubtful  by  its 

1  Ann.  Chcm.  Pharm.  xliii.  108. 

2  Phil.  Mag.  xx.  501. 

3  Journ.  Prakt.  Chcm.  xxxv.  309. 

4  Frerichs  and  Wohler,  Ann.  Chcm.  Pharm.  Ixviii.  336. 

6  Erdmannand  Marchand,  Journ.  Prakt.  Chem.  xxvi.  491. 

6  E.  and  H.  Salkowski,  Ber.  Deutsch.  Chem.  Ges.  xii.  653. 

7  Grabe  and  Schultzen,  Ann.  Chcm.  Pharm.  cxlii.  349. 

8  Lautetnann,  ibid.  cxxv.  12. 

9  Nauyen  and  Schultzen,  Zeitschr.  Chem.  1868,  29. 

0  E.  and  H.  Salkowski,  loc.  cit. 

1  Bertagnini,  Ann.  Chem.  Pharm.  xcvii.  249. 

12  Kraut,  ibid,  xcviii.  360. 

13  Grabe  and  Schultzen,  loc.  cit. 


186  AROMATIC  COMPOUNDS. 

different  crystalline  form."  These  fragrant  grasses  were  after- 
wards found  to  contain  not  benzoic  acid  but  coumarin,  C9H602, 
which  is  the  anhydride  of  orthohydroxyphenylacrylic  acid, 
C6H4(OH)C2H2.C02H. 

After  it  had  been  proved  that  benzoic  acid  and  allied  sub- 
stances are  converted  into  hippuric  acid  in  the  organism,  it 
seemed  probable  that  that  occurring  in  the  urine  of  graminivora 
would  be  derived  from  benzoic  acid  or  other  benzoyl  compounds 
occurring  in  the  fodder.  Hallwachs,  therefore,  investigated  the 
chief  grasses  and  plants  in  question,  but  was  unable  to  detect  the 
slightest  trace  of  benzoic  acid  or  any  other  compound  which 
could  yield  hippuric  acid ;  he  also  showed  that  coumarin  and 
chlorophyll,  which  might  be  looked  upon  as  allies  of  the  benzoyl 
series,  pass  through  the  organism  unchanged.1 

O.  Loew  found,  however,  that  quinic  acid,  which  occurs  in 
many  plants,  is  also  present  in  hay,  and  considered  it  to  be  the 
source  of  the  hippuric  acid.2  Although  the  latter  acid  can  be 
obtained  from  quinic  acid,  it  passes  through  the  organism 
almost  unchanged,  only  a  very  small  portion  being  converted 
into  hippuric  acid.3 

The  amount  of  hippuric  acid  in  the  urine  is  naturally  greater 
when  such  fruits  as  plums  and  cranberries,  which  contain  benzoic 
acid,  have  been  eaten;4  but  Ducheck  found  a  much  larger  quantity 
than  would  correspond  to  the  amount  of  benzoic  acid  contained 
in  the  plums. 

As  already  mentioned,  hippuric  acid  occurs  largely  in  the 
urine  of  diabetic  patients  who  subsist  on  a  meat  diet,  and  in 
that  of  others  who  have  passed  several  days  without  taking  food, 
as  well  as  in  small  quantity  in  the  urine  of  dogs  after  a  meat 
diet  or  long  fasting. 

It  follows  from  these  facts  with  tolerable  certainty  that  the 
hippuric  acid,  or  rather  the  aromatic  group  contained  in  it,  is 
derived  from  the  albuminoids,  which  are  known  to  yield  benz- 
aldehyde  and  benzoic  acid  on  oxidation,  while  phenylpropionic 
acid  is  formed  from  them  by  the  pancreatic  fermentation  (E.  and 
H.  Salkowski). 

E.  Salkowski  has  adduced  a  further  proof  for  this  in  the  fact 
that  phenylaceturic  acid,  (C6H5.CH2.CO)NH.CH2.CO2H,  which 
is  the  homologue  of  hippuric  acid,  occurs  in  horses'  urine  and 

^  Ann.  Chcm.  Pharm.  cv.  207.  "  Journ.  Prakt.  Chem.  [2]  xix.  309. 

3  Stadelmann,  Jahresber.  Chem.  1879,  982. 

4  Ducheck,  Gmeliris  Org.  Chem.  v.  332  ;  Thudichum,  Jahresber.  Chem.  1863, 
656. 


PREPARATION  OF  HIPPURIC  ACID.  187 

can  readily  be  split  up  into  glycocoll  and  phenylacetic  acid, 
C6H5.CH2.C02H.  The  latter  acid  is  also  formed,  together  with 
phenylpropioriic  acid,  by  the  putrefraction  of  albumen.1 

The  source  of  the  hippuric  acid  is  therefore  identical  with  that 
of  the  uric  acid,  which  is  especially  formed  in  the  organism  of 
the  carnivora. 

21 10  The  acid  is  best  prepared  from  the  urine  of  cows  or 
oxen,  which  often  contains  such  a  large  quantity  that  it  is  preci- 
pitated by  the  addition  of  hydrochloric  acid.  If  this  be  not  the 
case,  the  urine  is  boiled  up  with  milk  of  lime,  filtered,  and  the 
filtrate  neutralized  with  hydrochloric  acid,  evaporated,  and  then 
treated  with  an  excess  of  hydrochloric  acid.2  Putz  proposes  to 
precipitate  the  neutral  solution  with  ferric  chloride  and  decom- 
pose the  washed  precipitate  with  hydrochloric  acid.3  The  acid 
obtained  by  these  methods  is  always  discoloured,  but  the  im- 
purity may  be  removed  by  dissolving  it  in  warm  chlorine  water,4 
or  treating  its  aqueous  solution  with  bleaching  powder.5  It  is 
more  convenient  to  effect  the  purification  by  allowing  3  parts 
of  the  acid  to  stand  in  contact  with  1  part  of  nitric  acid,  of 
sp.  gr.  To,  and  filtering  off  the  mother-liquor  after  twenty- 
four  hours.6  It  can  also  be  dissolved  in  hot,  dilute  caustic  soda 
solution  and  treated  with  potassium  permanganate  until  yellow 
crystals  separate  out  on  the  addition  of  hydrochloric  acid.7 
These  are  boiled  with  water  and  animal  charcoal  and  then 
finally  re-crystallized  from  hot  water. 

Hippuric  acid  is  also  readily  obtained  when  finely  powdered, 
dry  amido-acetic  acid  is  gradually  added  to  an  excess  of  heated 
benzoic  anhydride,  and  the  mixture  heated  on  an  oil-bath  until 
it  becomes  coloured  red.  It  is  then  allowed  to  cool,  dissolved 
in  water  and  neutralized  with  caustic  soda,  the  solution  being 
subsequently  acidified  with  hydrochloric  acid  and  allowed  to 
stand  for  several  days.  The  precipitated  hippuric  acid  is  boiled 
with  water  and  animal  charcoal,  the  filtrate  concentrated  on  the 
water-bath  and  then  allowed  to  cool  slowly.  The  large  crystals 
which  are  formed  are  then  washed  with  petroleum  spirit  to 
remove  any  adhering  benzoic  acid.8 

1  Ber.  Dcutsch.   Chem.   Ges.  xvii.  3010. 

2  Gregory,  Ann.  Chem.  Pharm.  Ixiii.  125. 

3  Jahrcsber.  Chem.  1877,  795. 

4  Dauber,  Ann.  Chem.  Pharm.  Ixxiv.  202. 

5  Conrad,  Journ.  PraJct.  Chem.  [2]  xv.  244. 

6  Hutstein,  Jahrcsb.  1854,  453 

7  Gossmann,  Ann.  Chem.  Pharm.  xcix.  374  ;  Conrad,  loc.  cit. 

8  Curtius,  Ber.  Dcutsch.  Chem.  Ges.  xvii.  1662. 


188  AROMATIC  COMPOUNDS. 

Properties. — It  forms  long,  lustrous,  rhombic  prisms  or  needles 
(Fig.  1),  which  are  sometimes  opaque,  and  which  dissolve  in  600 
parts  of  water  at  0° ;  it  is  only  slightly  soluble  in  cold  alcohol  and 
ether,  but  dissolves  readily  in  warm  water  and  alcohol.  It  is  in- 
soluble in  petroleum  spirit,  and  can  be  separated  from  benzoic 
acid  by  means  of  this  property.  It  reddens  litmus,  but  has  not 
a  sour  taste,  melts  at  187'5°  (Conrad)  and  decomposes  at  tem- 
peratures above  240°,  with  formation  of  hydrocyanic  acid,  benzoic 
acid,  benzonitril,  and  a  black,  resinous  substance.1  When  it  is 
heated  with  caustic  potash  to  260°,  ammonia  and  benzonitril  are 
given  off,  while  calcium  carbonate,  calcium  benzoate  and  carbon 
remain  behind.  Caustic  baryta  effects  a  similar  decomposition, 


FIG.  i. 


barium  cyanate  being  formed  in  addition,  while  when  an  excess 
of  baryta  is  employed,  benzene,  ammonia  and  methylamine  are 
given  off  and  barium  carbonate  and  benzoate  formed,  but  no 
cyanide.2  It  has  been  already  mentioned  that  on  heating  with 
strong  acids  or  alkalis  it  decomposes  into  benzoic  acid  and 
glycocoll ;  these  products  are  also  formed  when  it  is  heated  to 
120°  with  a  concentrated  solution  of  zinc  chloride  ;  when,  how- 
ever, it  is  distilled  with  anhydrous  zinc  chloride,  benzonitril  and 
carbon  dioxide  are  formed.3 

On  oxidation  with  lead  dioxide  and  sulphuric  acid  or  with 


1  Limpricht  and  Uslar,  Ann.  Chem.  Pharm.  Ixxxviii.  133. 

2  Kraut,  Jahresber,  1863,  348  ;  Conrad,  loc.  cit. 

3  Gossmann,  Ann.  Chem.  Pharm.  c.  69. 


the 


THE  HIPPURATES. 

... — . 

*ic  acid,  it  is  converted  into  hipparaffin  or  methylenedibenz- 
amide  (p.  175) : 

CH2.NH(CO.C6H5) 

C02H 

The  substitution  products  of  hippuric  acid  will  be  described 
among  the  corresponding  derivatives  of  benzoic  acid. 

21 1 1  The  Hippurates.  Hippuric  acid  decomposes  carbonates 
dissolves  zinc  with  evolution  of  hydrogen.  Its  salts  are  for 

e  most  part  soluble  in  water  and  crystallize  well ;  they  have 
been  investigated  by  Schwarz.1 

Potassium  hippurate,  C9H8KNO3  +  H20,  forms  vermicular 
crusts  consisting  of  pointed  rhombic  prisms ;  on  heating  it  forms 
a  vapour  which  possesses  a  smell  resembling  that  of  Satureja 
hortensis.  It  combines  with  hippuric  acid  forming  the  acid  salt, 
C9H8KN03  +  C9H9NO3  +  H2O,  which  crystallizes  in  quadratic 
tablets  possessing  a  satin  lustre. 

Sodium  hippurate,  4C9H8NaNO3  -f-  H2O,  is  a  crystalline  mass 
which  readily  dissolves  in  water  and  hot  alcohol. 

Acid  ammonium  hippurate,  C9H8(NH4)N03+C9H9NO3-fH2O, 
crystallizes  in  small,  quadratic  prisms  ;  the  normal  salt  has  not 
n  prepared. 

Calcium  hippurate,  (C9H8N03)2Ca  4-  3H2O,  forms  rhombic 
prisms,2  which  are  soluble  in  18  parts  of  cold  and  6  parts  of 
boiling  water  (Liebig). 

Strontium  hippurate,  (C9H8NO3)2Sr  +  5H20,  crystallizes  in 
fascicular  aggregates,  composed  of  four-sided  prisms ;  it  is  only 
slightly  soluble  in  cold  water  and  alcohol,  but  dissolves  readily 
in  them  when  hot. 

Barium  hippurate,  (C9H8N03)2Ba-hH20,  crystallizes  in  crusts 
made  up  of  quadratic  prisms.  Schwarz,  in  endeavouring  to 
separate  a  mixture  of  hippuric  and  benzoic  acids  by  means  of 
their  barium  salts,  obtained,  first,  barium  benzoate,  then  barium 
hippurate,  and,  finally,  from  the  mother-liquor,  the  double  salt, 
C7H502.Ba.C9H8N034-  5H2O,  in  characteristic  warty  masses.3 

Magnesium  hippurate,  (C9H8NO3)2Mg  +  5H2O,  forms  warty 
crystals. 

Zinc  hippurate,   (C9H8N03)2Zn  +  5H2O,    crystallizes  in  small 

1  Ann.  Chem.  Pharm.  liv.  33. 

2  Schabus,  Jahresber.  Chem.  1850,  411. 
8  Ann.  Chem.  Pharm.  Ixxv.  192. 


•"V 

1 


190  AROMATIC  COMPOUNDS. 

plates,  which  after  dehydration  dissolve  in  5 3' 2  parts  of  water  at 
17 '5°,  and  in  4  parts  at  1000.1 

Lead  hippurate,  (C9H8NO3)2Pb  +  2H20,  is  a  curdy  precipitate 
crystallizing  from  a  large  quantity  of  hot  water  in  fine,  silky 
needles,  which  often  suddenly  take  up  a  molecule  of  water 
arid  change  into  lustrous,  four-  sided  tablets. 

Copper  hippurate,  (C9H8N03)2Cu  +  3H2O,  is  slightly  soluble 
in  cold  water,  more  readily  in  hot  alcohol,  and  crystallizes  in 
small,  pointed,  rhombic  prisms  of  a  blue  colour. 

Silver  hippurate,  2C9H8AgN03  +  H2O,  is  a  curdy  precipitate, 
which  crystallizes  from  hot  water  in  aggregates  of  lustrous 
needles. 

When  ferric  chloride  is  added  to  a  solution  of  a  normal 
hippurate,  a  -cream-coloured  precipitate  of  ferric  hippurate  is 
thrown  down,  which  contains  more  or  less  basic  salt  according 
to  the  greater  or  less  dilution  of  the  solution  ;  this  fact  was  dis- 
covered by  Putz,  who  employed  the  compound  for  the  prepara- 
tion of  hippuric  acid  from  urine.  It  is  almost  insoluble  in 
pure  water,  but  dissolves  in  presence  of  free  hippuric  acid,  an 
excess  of  ferric  chloride  and  in  alcohol.  Wreden  has  proposed 
to  employ  this  reaction  for  the  determination  of  hippuric  acid  in 
urine.  Henneberg,  Stohmann,  and  Rautenberg,  found  that  it  is 
most  convenient  for  this  purpose  to  make  use  of  a  solution  of 
ferric  nitrate  which  has  been  standardized  with  pure  hippuric 
acid.  The  urine  is  acidified  with  nitric  acid,  heated  to  boiling 
to  remove  carbon  dioxide,  neutralized  with  calcium  carbonate, 
treated  with  an  excess  of  lead  nitrate,  and  then  diluted  to  a 
known  volume  and  filtered.  An  aliquot  portion  of  the  filtrate 
is  heated  and  titrated  with  the  ferric  nitrate  solution  until  a 
drop  of  the  clear  liquid  gives  a  blue  colouration  with  potassium 
ferrocyanide,  the  distinction  between  this  and  the  white  of  the 
lead  ferrocyanide  which  is  formed  at  first,  being  very  sharp.2 

Methyl  hippurate,  C9H8(CH3)NO3,  is  obtained  by  the  action 
of  hydrochloric  acid  on  a  hot  solution  of  hippuric  acid  in  methyl 
alcohol.3  It  is  slightly  soluble  in  cold,  more  readily  in  hot  water 
and  in  alcohol,  and  crystallizes  in  long,  white  prisms,  which  melt 
at  80'5°,  and  decompose  at  250°  with  formation  of  ammonia  and 
benzonitril. 

Ethyl   hippurate,   C9H8(C2H5)NO3,   is    formed    in    a   similar 

1  Lowe,  Jahrcsber.  1855,  536.  2  Ann.  Chem.  Pharm.  cxxiv.  182. 

3  Jaqucmin  and  Schlagdenhauffen,  Compt.  Rend.  xlv.  1011  ;  Conrad,  Journ. 
Prakt.  Chem.  [2]  xv.  247. 


THE  HIPPURATES.  191 


manner  to  the  methyl  ether,1  and  also  by  allowing  a  saturated, 
warm  alcoholic  solution  of  hippuric  acid  to  stand  for  a  month  in 
a  warm  place.2 

It  may  also  be  readily  prepared  by  heating  ethyl  amido-acetate 
with  benzoic  anhydride  to  100°.3  It  crystallizes  from  hot  water 
in  long,  white,  silky  needles,  which  melt  at  60'5°,  have  no  odour, 
but  a  sharp  taste  resembling  that  of  oil  of  turpentine,  and  de- 
compose on  heating.  On  distillation  with  steam,  it  decomposes 
into  alcohol  and  the  free  acid. 

The  following  ethers  have  also  been  prepared  : 4 

Melting- 
point. 

Butyl  hippurate,  C9H8(C4H9)N03,  prisms 40°— 41° 

Isobutyl  hippurate,  C9H8(C4H9)N03  small,  rhombic 

prisms 45° — 46° 

Amyl  hippurate,  C9H8(C6HU)N08>  small  needles  .    .  27°— 28° 

When  hippuric  acid  is  distilled  with  phosphorus  pentachloricle, 
hydrochloric  acid  is  evolved  and  the  distillate  consists,  first,  of 
phosphorus  oxychloride,  then  of  benzoyl  chloride  and  finally  of 
the  compound  C9H6C1NO,  which  crystallizes  from  ether  in  flat, 
four-sided,  monoclinic  prisms,  melting  at  40° — 50°.  It  boils  at 
220°,  is  not  attacked  by  alcoholic  potash,  and  on  fusion  with 
potash  yields  benzoic  acid  and  ammonia.5  The  formation  of  this 
substance  may  be  explained  by  the  following  equations : 

CH0.NH.CO.C6H5  CH2.NH.CO.C6H5 

+2PC15=  |  +  2POC13+HC1. 

CO.OH  CC13 


CH9.NH.CO.C6H5 

I  =||      >N.CO.C6H5  +  2HC1. 

CC13  CC1/ 

Hippuramide,  (C6H5.CO)NH.C2H2O.NH2,  is  formed  by  the 
action  of  aqueous  ammonia  on  the  ethyl  ether;  it  separates 
from  hot  water  in  short,  thick  crystals,  melting  at  183°  (Jaque- 
min  and  Schlagdenhauffen  ;  Conrad). 

Hippuramido-acetic  acid,  CUH12N2O4,  is  formed,  together 
with  hippuric  acid,  by  the  action  of  benzoyl  chloride  on  silver 

1  Stenhouse,  Ann.  Chem.  Pharm.  xxi  148  ;  Conrad,  loc.  cit. 

2  Liebig,  Ann.  Chem.  Pharm.  Ixv.  351. 

3  Curtius,  Ber.  Dcutsch.  Chem.  Gcs.  xvii.  1662. 

4  Campani  and  Bizzarri,  Bull.  Soc.  Chim.  xxxv.  427  ;  Carapani,  Ber    Dcutsch. 
Chem.  Gcs.  xi.  1247. 

5  Schwanert,  Ann.  Chem.  Pharm.  cxii.  59. 


192  AKOMATIC  COMPOUNDS. 

amido-acetate,  and  is  probably  derived  from  the  hippuric  acid 
which  is  first  formed  : 

CH2,NH.CO.C6H5  CH2.NH.CO.C6H, 

|  +  NH2.CH2.CO.OH  =  | 

CO.OH  CO.NH.CH.,.CO.OH 

+  H20 

It  crystallizes  from  hot  water  in  rhombic  tablets  or  needles, 
melting  at  206'5°.  On  boiling  with  hydrochloric  acid,  it  decom- 
poses into  amido-acetic  acid  and  benzoic  acid ;  on  heating  with 
dilute  acids,  on  the  other  hand,  both  hippuric  acid  and  amido- 
acetic  acid  are  formed.  Its  salts  crystallize  well;  the  ethyl 
ether,  which  melts  at  117°,  combines  with  ammonia  forming 
hippurglycollamide,  which  crystallizes  in  large,  transparent  plates, 
melting  at  202°. 

An  acid,  C10H12N304,  is  also  formed  by  the  reaction  just  men- 
tioned, and  crystallizes  from  hot  water  in  microscopic  needles 
which  melt  at  240°,  and  are  decomposed  by  hot  hydrochloric  acid 
into  amido-acetic  acid,  benzoic  acid,  and  a  non-crystallizable, 
nitrogenous  compound.1 

Hydrobenzuric  acid,  C18H24N2O6,  is  obtained  by  the  action  of 
sodium  amalgam  on  a  concentrated  solution  of  hippuric  acid  in 
caustic  soda  solution ;  it  forms  a  mass  resembling  turpentine, 
and  becomes  crystalline  after  standing  for  months.  When  it  is 
treated  with  an  excess  of  sodium  amalgam  and  water,  it  decom- 
poses into  hydrobenzyluric  acid,  C16H21NO4,  and  amido-acetic 
acid.  The  former  is  an  oily  liquid,  which  gradually  solidifies ; 
on  boiling  with  alkalis  it  decomposes  into  hydrobenzoic  acid, 
benzyl  alcohol  and  amido-acetic  acid.  Its  alkaline  solution 
oxidizes  in  the  air  with  formation  of  hydroxybenzyluric  acid, 
C16H2]NO5,  which  is  a  crystalline  mass  melting  at  60° — 70°.2 

2 1 12  Ornithuric  acid,  C19H20N2O4.  Shepard  found  that  ben- 
zoic acid  is  not  converted  into  hippuric  acid  in  the  organism  of 
birds,  but  into  another  nitrogenous  compound,  which  was  more 
closely  examined  by  JafFe.3  He  obtained  it  from  the  excre- 
ments of  hens  which  were  fed  with  benzoic  acid;  it  is  very 
slightly  soluble  in  water  and  crystallizes  from  hot  alcohol  in 
minute  needles,  melting  at  182°.  Its  solution  reddens  litmus. 
The  following  salts  are  characteristic  : 

1  Curtius,  Journ.  Prakt.  Chem.  [2]  xxvi.  145. 

2  Otto,  Ann.  Chem.  Pharm.  cxxxiv.  303. 

8  Jaffe,  Ber.  Deutsch.  Chem.  Ges.  x.  1925  ;  xi.  406. 


ORNITHINE. 


193 


Calcium  ornithurate,  (C19H19~N"2O4)2Ca,  is  obtained  by  adding 
the  ammonium  salt  to  a  solution  of  calcium  chloride  and  heating 
the  mixture  ;  it  is  a  crystalline  precipitate,  which  is  only  very 
slightly  soluble  in  water. 

Barium  ornithurate,  (C19H19N2O4)2Ba,  is  exceptionally  soluble 
in  water  and  alcohol,  and  is  deposited  from  its  alcoholic  solution 
in  opaque,  crystalline  flocks,  which  after  drying  form  a  snow- 
white  powder. 

On  boiling  the  acid  with  hydrochloric  acid,  it  decomposes 
almost  immediately  into  benzoic  acid  and  lenzoylornithine, 
C^HjgN^Og,  which  is  almost  insoluble  in  alcohol  and  crystallizes 
from  water  in  very  brittle  needles,  melting  at  225°  — 230°.  It 
forms  readily  soluble  salts  with  the  mineral  acids. 

If  the  boiling  with  hydrochloric  acid  be  continued  for  some 
time,  the  acid  decomposes  into  benzoic  acid  and  ornithine, 
C5H12N202,  which  is  very  deliquescent,  has  a  strongly  alkaline 
reaction  and  a  somewhat  caustic  taste.  It  combines  with  acids 
to  form  salts  which  crystallize  well. 

Ornithine  has  the  composition  of  a  diamidovalerianic  acid,  and 
the  constitution  of  these  compounds  can  therefore  be  expressed 
by  the  following  formulae  : 


Ornithine. 

NH2 

C4H7.C92H 

NH0 


Benzoylornithine. 

NH2 

C4H7.C02H 

NH.CO.C6H5 


Ornithuric  acid. 

NH.CO.C6H5 

C4H7.C02H 
I 
NH.CO.C6H5. 


Free  ornithine,  which  has  an  alkaline  reaction,  will,  of  course, 
ive  the  following  formula  : 

NH2 

C4H7.CO 

I        I 
NH3.0 


194  AROMATIC  COMPOUNDS. 


BENZENYL   COMPOUNDS. 

2113  These  compounds  are  closely  allied  to  the  benzoyl  deriva- 
tives. Phosphorus  chloride  converts  benzoic  acid,  C6H5.CO.OH, 
first  into  benzoyl  chloride,  C6H5.COC1,  and  then  by  further 
action  into  benzenyl  chloride,  C6H5.CC13.  The  latter  is  also 
formed  by  the  continued  action  of  chlorine  on  boiling  toluene ; 
on  heating  with  caustic  potash  it  is  reconverted  into  benzoic 
acid,  which  therefore  bears  the  same  relation  to  it  as  formic 
acid  to  chloroform.  The  action  of  the  potash  is  probably  to  form 
benzenyl  alcohol  or  orthobenzoic  acid  in  the  first  instance  : 

C6H5.CC13+3KOH^:C6H5.C(OH)3  +  3KC1. 

This  is,  however,  as  unstable  as  orthoformic  acid  and  immedi- 
ately decomposes  into  water  and  benzoic  acid  ;  ethers  are,  how- 
ever, known,  such  as  ethyl  orthobenzoate,  C6H5.C(OC2H5)3, 
obtained  by  the  action  of  sodium  ethylate  on  benzenyl  tri- 
chloride. 

Benzoic  acid  itself  may,  therefore,  be  looked  upon  as  a  benzenyl 
compound,  and  this  view  was  actually  taken  by  Berzelius 
(Part  I.,  p.  12). 

A  large  number  of  compounds  which  are  formed  by  the 
action  of  hydroxylamine  on  benzoyl  chloride  may  also  be  in- 
cluded among  the  benzenyl  derivatives.  The  simplest  of  these  is 
benzyhydroxamic  acid : 

^N.OH 

\OH. 

Benzonitril,  C6H5.CN,  and  its  compounds  with  alcohols,  such 
as  benzimido-ethyl  ether : 

^H 

XOC2H5. 

also  belong  to  this  class.      The   latter  compound  is  converted 
by  ammonia  into  benzenylamidine  or  benzimido- amide : 

^H 
\NH2. 


BENZENYL  TRICHLORIDE.  195 

Benzenyl  amidines  which  contain  the  radical  phenyl,  &c.,  are 
obtained    by    heating   benzonitril    with    the    hydrochlorides    of 
ido-bases  ;  thus  aniline  yields  phenylbenzenylamidine  : 


C6H6.C; 


N(C6H6)H. 


Another  series  of  amidines  (Part  III.,  p.  216)  consists  of  the 
anhydro-bases,  which  are  formed  from  the  orthoamido-compounds 
by  the  elimination  of  water;  benzoylorthodiamidobenzene  in 
this  way  yields  phenylenebenzenylamidine  : 


Benzenyl  trichloride  or  Benzo-trichloride,  C6H5.CC13.  Liebig 
d  Wohler  found  during  their  researches  on  the  radical  of 
zoic  acid,  that  benzoyl  chloride  is  converted  by  phosphorus 
tachloride  into  a  strongly-smelling,  oily  substance,  which  they 
did  not  investigate  more  closely.1  It  was  made  the  subject  of 
research  by  Schischkow  and  Rosing2  and  also  by  Limpricht,3 
who  found  that  it  is  also  formed  when  benziderie  dichloride, 
C6H5.CHC12,  is  treated  with  chlorine,  and  named  it  benzoic 
trichloride.  Benzenyl  trichloride  is  most  readily  obtained  by 
passing  chlorine  into  boiling  toluene  until  no  further  increase  in 
weight  takes  place.4  The  product  is  then  washed  with  caustic 
soda  solution,  dried  over  ignited  potassium  carbonate  and  recti- 
fied ;  it  is  employed  in  the  colour  industry  and  is  manufactured 
on  the  large  scale,  being  purified  by  distillation  in  a  vacuum. 

Benzenyl  trichloride,  which  is  also  known  as  phenylchloroform, 
is  a  powerfully  refractive  liquid,  which  has  a  characteristic 
penetrating  odour,  boils  at  213° — 214°,  and  has  a  sp.  gr.  of 
1'380  at  14°.  On  heating  with  water  to  150°,  it  is  converted 
into  benzoic  acid,  while  benzoic  anhydride  is  formed  when  it  is 
heated  with  sulphuric  acid  which  contains  4'6  per  cent,  of  water 
ij).  166).  It  is  decomposed  by  fuming  nitric  acid  with  formation 
of  metanitrobenzoic  acid  (Beilstein  and  Kuhlberg). 

1  Ann.  Chem.  Pkarm.  iii.  265. 

2  Jahrcsbcr.  Chem.  1858,  279. 

1  Ann.  Chem.  Pharm.  cxxxiv.  55  ;  cxxxv.  80  ;  cxxxix.  323. 
4  Beilstein  and  Kuhlberg,  ibid,  cxlvi.  330. 


198  AROMATIC  COMPOUNDS. 

Benzenyl  tribromide,  C6H5.CBr3,  is  formed  by  the  action  of 
bromine  on  boiling  toluene,  and  is  a  colourless  liquid  which  has 
an  exceedingly  violent  action  on  the  eyes  and  mucous  mem- 
brane. It  cannot  be  distilled,  since  it  decomposes  at  about 
150° ;  on  heating  with  water  it  is  readily  converted  into  benzoic 
acid,  while  it  is  only  very  slowly  attacked  by  boiling  alcohol.1 

Benzcnyl  ethyl  ether,  C6H5.C(OC2H5)3.     This  compound,  which   j 
is  also  called  ethyl  orthobenzoate,  was  obtained  by  Limpricht,  j 
who  heated  the  chloride  to  100°  with  a  solution  of  sodium  in 
absolute  alcohol.     It  is  a  transparent,  colourless  liquid,  which 
smells  like  ethyl  benzoate  and  boils  at  220°  — 225°. 

Benzenyl  triacetate,  C6H5.C(OC2H3O)3,  is  formed  by  the  action 
of  silver  acetate  on  the  chloride,  and  is  a  liquid  which  decom- 
poses on  distillation  into  acetic  anhydride  and  benzoic  an- 
hydride. If  it  be  allowed  to  stand  in  the  air  or  over  sulphuric 
acid  in  a  vacuum,  white  needles  separate  out,  which  melt  at 
70°,  and  have  the  composition  of  acetobenzoic  anhydride 
(Limpricht). 

Monochlorobenzenyl  trichloride,  C6H4C1.CC13.  The  ortho- 
compound  has  been  obtained  by  the  action  of  phosphorus  penta- 
chloride  on  salicylic  acid,  C6H4(OH)C02H ;  it  is  crystalline, 
melts  at  30°  and  boils  at  2600.2  The  meta-compound  has  been 
prepared  in  a  similar  manner  from  metasulphobenzoic  acid, 
C6H4(SO3H)CO.2H,  and  boils  at  235° ; 3  the  para-compound  is 
formed  by  the  chlorination  of  benzenyl  trichloride  in  presence  of 
iodine  ;  it  boils  at  245°  and  yields  parachlorobenzoic  acid  when 
heated  with  water  to  200°  (Beilstein  and  Kuhlberg). 

Dichlorobcnzenyl  trichloride,  C6H3C12.CC13,  has  been  prepared 
by  the  action  of  chlorine  on  a  boiling  mixture  of  the  dichloro- 
toluenes  obtained  by  chlorinating  toluene.  The  product  boils 
at  273° — 280°  and  yields  three  dichlorobenzoic  acids  on  heating 
with  water.4 

Trichlorobenzenyl  trichloride,  C6H2C13.CC13,  is  formed  by  pass- 
ing chlorine  into  boiling  trichlorotoluene  ;  it  crystallizes  from 
alcohol  in  very  fine  needles,  melts  at  82°  and  boils  at  307°— 308°. 

Tctrachlorobenzcnyl  trichloride,  C6HC14.CC13,  forms  fine,  short 
needles,  melts  at  104°  and  boils  at  3160.5 

1  Tnce,  Abst.  Proc.  Chem.  Soc.  1885-6,  131. 

2  Kolbe  and  Lautemann,  Ann.  Chem.  Pharm.  cxv.  195. 

3  Carius  and  Kammerer,  ibid,  cxxxviii.  58. 

4  Schulz,  ibid,  clxxxvii.   260 ;  Aronheim  and  Dietrich,  Bcr.   Deutsch.   Chem. 
Ges.  viii.  1401. 

8  Beilstein  and  Kuhlberg,  Ann.   Chem.  Pharm.  cl.  286. 


BENZONITRIL. 


BENZONITRIL   AND   ITS  DERIVATIVES. 

2114  Benzonitril,  C6H5.CN.  This  substance  was  prepared  by 
Liebig  and  Wohler  by  heating  benzamide  with  baryta,1  but  was 
not  investigated  by  them,  and  its  identity  with  the  benzonitril 
discovered  by  Fehling  was  established  at  a  much  later  period. 
The  latter  chemist  obtained  it  by  the  dry  distillation  of  ammo- 
nium benzoate,2  from  which  it  is  formed  by  loss  of  water. 
It  can  be  prepared  by  a  similar  reaction  from  benzamide, 
C6H5.CO.NH2,  by  heating  it  with  phosphorus  pentoxide,3  phos- 
phorus pentachloride,4  phosphorus  pentasulphide,5  benzoyl  chlo- 
ride,6 potassium  benzoate,7  or  caustic  lime.8 

Among  many  other  methods  of  preparation,  some  of  which 
have  been  already  mentioned  (Part  III.,  p.  31),  the  following 
are  the  most  important.  It  can  readily  be  obtained  by  distilling 
two  molecules  of  benzoic  acid  with  one  molecule  of  potassium 
thiocyanate : 

C6H6.C02H  +  HSCN  =  C6H5.CN  +  CO2  +  H2S. 

One  half  of  the  benzoic  acid  is  converted  into  the  potassium 
salt,  from  which  it  can  readily  be  recovered.9 
Lead  thiocyanate  may  be  substituted  for  the  potassium  salt : 10 

2CCH5.C02H  +  Pb(SCN)2  =  2C6H5.CN  +  PbS  +  H2S  +  2C02. 

Benzonitril  is  synthetically  prepared  by  the  distillation  of 
sodium  benzenesulphonate  with  potassium  cyanide,11  as  well  as 
by  heating  iodobenzene  to  350°  with  silver  cyanide,12  or  by  the 
action  of  cyanogen  chloride  on  benzene  in  presence  of  aluminium 
chloride.13  It  is  obtained  from  aniline  by  converting  the  latter 
into  diazobenzene  chloride  and  heating  this  with  a  solution  of 

Wohler,  Ann.  Chem.  Pharm.  cxcii.  362.  2  Ibid.  xlix.  91. 

Hofmann  and  Buckton,  ibid.  c.  155. 

Gerhardt,  Chim  Org.  iv.  762  ;  Henke,  Ann.  Chem.  Pharm,  cvi.  276. 

Henry,  Bcr.  Deutsch.  Chem.  Ges.  ii.  307. 
(  Sokolow,  Gerhardt' s  Org.  Chim.  i.  386. 

Kekule,  Bcr.  Deutsch.  Chem.  Ges.  vi.  113. 

Anschiitz  and  Schulz,  Ann.  Chem.  Pharm.  cxcvi.  48. 

Letts,  Bcr.  Deutsch.  Chem.  Ges.  v.  673. 
10  Kriiss,  ibid.  xvii.  1766 

1  Merz,  Zeitschr.  Chem.  1868,  33  ;  Ber.  Deutsch.  Chem.  Ges.  iii.  710. 

2  Merz  and  Weith,  ibid.  x.  746. 

13  Friedel  and  Crafts,  Bull.  Soc.  Chim.  xxix.  2. 

244 


198  AROMATIC  COMPOUNDS. 

the  double  cyanide  of  potassium  and  copper.1  It  can  easily  be 
prepared  in  the  pure  state  by  distilling  benzamide  with  phos- 
phorus pentoxide  and  rectifying  the  product  over  the  latter.  A 
good  yield  is  obtained  by  Letts's  process,  according  to  which  the 
mixture  of  benzoic  acid  and  potassium  thiocyanate  is  heated  in 
an  apparatus  connected  with  an  inverted  condenser  until  a 
white,  solid  mass  has  been  formed.  The  product  is  then  dis- 
tilled, the  distillate  freed  from  benzoic  acid  by  means  of  ammonia, 
and  the  benzonitril  finally  distilled  in  steam  ;  he  thus  obtains  80 
per  cent,  of  the  theoretical  yield.  Merz,  by  the  distillation  of 
500  grms.  of  sodium  benzenesulphonate  with  330  grins,  of 
potassium  cyanide,  obtained  in  one  case  130  and  in  another  140 
grms.  of  the  crude  80  per  cent,  nitril,  while  Henry,  employing 
his  own  method,  obtained  half  the  theoretical  yield. 

Properties. — Benzonitril  is  a  mobile  liquid,  which  smells  like  oil 
of  bitter  almonds,  has  a  sp.  gr.  of  T023  at  0°,  boils  at  191°  and 
solidifies  in  a  mixture  of  ether  and  solid  carbon  dioxide  to  a  crystal- 
line mass,  melting  at  —  1 7°.2  It  is  miscible  with  alcohol  and  ether, 
and  dissolves  in  about  100  parts  of  water  (Fehling).  On  boiling 
with  caustic  potash  it  is  converted  into  benzoic  acid,  and  it  is  re- 
duced in  alcoholic  solution  by  zinc  and  hydrochloric  acid  to  benzyl- 
amine  (Mendius) ;  fuming  sulphuric  acid  in  the  cold  polymerizes 
it  to  cyanphenin,  but  on  heating,  forms  metasulphobenzoic  and 
benzenedisulphonic  acids  (Hofmann  and  Buckton).  When  it 
is  mixed  with  benzene  and  concentrated  sulphuric  acid,  dibenz- 
imido-oxide,  C14H12N2O,  is  obtained;  it  crystallizes  in  thick  vitre- 
ous prisms  and  has  basic  properties.3  On  heating  it  with  dilute 
hydrochloric  acid,  dibenzamide  is  formed.4  Both  substances  are 
obtained  when  well-cooled,  fuming  sulphuric  acid  is  allowed  to 
drop  into  benzonitril,  and  the  mixture  treated  with  water  after 
standing  for  some  time.5  Their  formation  is  explained  by  the 
following  equations : 

C6H5.CN  C6H5.COX 

+  H20  >NH 

C6H5.CN  C6H5.C4NH. 

C6H5.COX  C6H5CO 

>NH-f-H20    =  >NH+NHr 

C6H5.CdNH  C6H5CO/ 

1  Sandmeyer,  Bcr.  Deutsch.  Ckem.   Ges.  xvii.  2653. 

2  Hofmann,  Jahrcsber.  1862,  335. 

3  Klein  and  Pinner,  Her.  Dcutsch.  Chem.  Ges.  xi.  764. 

4  Pinner,  ibid.  xvii.  2006. 

6  Gumpert,  Journ.  Prakt.  Chem.  [2]  xxx.  87  ;  Pinner,  ibid.  xxx.  125. 


BENZONITRIL.  199 


When  benzonitril  is  shaken  up  with  a  warm  mixture  of  caustic 
potash  solution  and  hydrogen  peroxide,  it  is  rapidly  converted 
into  benzamide,  pure  oxygen  being  evolved : x 


V>  liiv 

± 

tt 


C6H5.CN  +  2H2O2=C6H5.CO.NH2  +  H2O  +  02. 

If  benzonitril  be  taken  internally,  it  appears  in  the  urine  in 
the  form  of  oxybenzonitrilsulphuric  acid,  C6H4(O.S03H)CN, 
which  readily  decomposes  into  sulphuric  acid  and  the  nitrils  of 

icylic  acid  and  parahydroxybenzoic  acid ;  the  meta-compound, 
ever,  is  not  formed.2 

Benzonitril  combines  with  hydrobromic  acid  to  form  the 
crystalline  compound,  C6H5.CN  +  2HBr,  which  is  converted  by 
water  into  benzamide  :  3 

C6H5.CBr2.NH2  +  H2O  =  C6H5.CO.NH2+ 2HBr. 

According  to  Henry,  a  similar  compound  is  formed  with 
hydriodic,4  but  not  with  hydrochloric  acid ;  when,  however,  a 
current  of  the  latter  gas  is  passed  into  an  ethereal  solution  of 
platinum  chloride  and  benzonitril,  long  needles  separate  out, 
which  decompose  in  dry  air  into  their  three  components.5 

When  benzonitril  is  heated  with  bromine,  the  monobromide, 
(C7H5NBr)2,  is  formed ;  it  crystallizes  from  ether  in  small 
needles,  which  partially  sublime  when  heated  and  are  partially 
decomposed  into  bromine,  benzonitril  and  cyanphenin  ;  while  on 
heating  with  lime,  some  carbon  dioxide  and  ammonia  are  evolved 
in  addition  to  the  compounds  mentioned.  A  dibromide  also 
appears  to  exist,  but  it  is  very  unstable.6 

It  combines  with  some  metallic  chlorides  to  form  the 
following  solid  compounds,  C7H5N,AuCl3,  (C7H5N)2PtCl4, 
(C7H5N)2SnCl4  and  (C7H5N)2TiCl4,  the  last  of  which  forms 
bright  crystals  which  may  be  sublimed.7 

2115  Cyanphenin,  C21H15N3.  This  compound,  which  corre- 
sponds to  cyanethin  (Part  I.,  p.  562),  was  obtained  by  Cloez 
by  heating  benzoyl  chloride  with  potassium  cyanate,8  and 
i  Engler  prepared  it,  as  already  mentioned,  from  benzonitril 

1  Radziszewski,  Ber.  Deutsch.  Chem.  Gfcs.  xviii.  355. 

2  Baumann,  ibid.  xvii.  Ref  256. 

3  Engler,  Ann.  Chem.  Pharm.  cxlix.  307. 

4  Bull.  Soc.  Chim.  vii.  85. 

5  Klein  and  Pinner,  Ber.  Deuisch.  Chem.  Ges.  x.  1891. 

6  Engler,  Ann.  Chem.  Pharm.  cxxxiii.  144. 

7  Henke,  ibid.  cvi.  284. 

8  Ibid.  cxv.  27. 


200  AROMATIC  COMPOUNDS. 

bromide.  Hofmann  found  that  it  is  formed  when  benzonitril 
is  heated  with  sodium,1  and  Klein  and  Pinner  when  it  is  treated 
with  fuming  sulphuric  acid.2  It  is  also  obtained  in  tolerable 
quantity,  according  to  Henry,  together  with  benzonitril,  by  the 
action  of  phosphorus  pentasulphide  on  benzamide,  and,  together 
with  an  oily  base,  C16H18N2,  the  hydrochloride  of  which,  C1GH1(, 
N2C1,  crystallizes  in  six-sided  tablets,  when  benzonitril  is  heated 
with  zinc  ethyl.3 

Cyanphenin  is  a  hard,  crystalline  substance,  which  melts  at 
231°,  sublimes  in  needles,  and  boils  above  350°.  It  is  insoluble 
in  water,  slightly  soluble  in  alcohol  and  ether,  more  readily  in 
carbon  disulphide  and  ethyl  iodide.  It  is  not  attacked  when 
heated  with  aqueous  or  alcoholic  potash,  but  is  converted  into 
benzoic  acid  by  heating  to  220°  4  with  fuming  hydriodic  acid, 
or  to  250°  with  concentrated  hydrochloric  acid  (Frankland  and 
Evans). 


BENZIMIDO-ETHERS. 

2116  The  Benzimido-ethers  include  the  compounds  which  are 
formed  by  the  action  of  hydrochloric  acid  on  a  mixture  of 
benzonitril  with  an  alcohol.  Of  these  compounds  the  isobutyl 
ether  has  been  more  fully  described ; 5  its  formation  is  preceded 
by  that  of  a  compound  which  forms  large,  lustrous  crystals, 
which  fume  in  moist  air  and  decompose  into  hydrochloric  acid, 
ammonium  chloride  and  isobutyl  benzoate  : 

/NH3C1 
C6H6.C^OC4H9-|-H2O  =  HC1+NH4C1+C6H5.CO.OC4H9. 

•M-tt 

If,  however,  the  compound  be  freed  from  benzonitril  and 
isobutyl  alcohol  by  washing  with  ether  and  allowed  to  stand 
over  caustic  soda,  a  molecule  of  hydrochloric  acid  is  given  off 
and  the  hydrochloride  of  benzimido-isobutyl  ether  remains 

1  Ber.  Deutsch.  Chem.  Ges.  i.  198. 

2  Ibid.  xi.  764  ;  Pinner,  Journ.  Prakt.  Chem.  [2]  xxx.  125. 
8  Frankland  and  Evans,  Journ.  Chem.  Soc.  1880,  i.  563. 

4  Engler,  Ann.  Chem.  Pharm.  cxlix.  310. 

8  Pinner  and  Klein,  Ber.  Deutsch.  Chem.  Ges.  x.  1889 ;  xi.  4. 


BENZIMIDO-ETHERS. 

it  decomposes  on  heating  into  benzamide  and  isobutyl 
chloride : 

,NH2C1 

C6H5.C^  =  C6H5.CO.NH2+C,H9CL 

OC4H9 

It  is  decomposed  by  a  solution  of  ammonia  in  absolute  alcohol, 
with  formation  of  the  free  isobutyl  ether,  ammonium  chloride 
and  benzenylamidine  hydrochloride. 

Benzimido-isobutyl  ether,  C6H5.C(NH)OC4H9,  is  a  thick,  oily 
liquid,  which  partially  decomposes  on  distillation ;  it  readily 
recombines  with  hydrochloric  acid ;  cold,  concentrated  sulphuric 
acid  converts  the  hydrochloride  into  the  acid  sulphate,  C6H5C 
(OC4H9)NH2.SO4H,  which  crystallizes  in  long,  pliant  needles. 

Benzimido-acetic  ether,  C6H5.C(NH)OC2H3O,  is  formed  by 
boiling  the  isobutyl  ether  with  acetic  anhydride ;  it  is  insoluble 
in  water  and  acids,  dissolves  in  alcohol  and  crystallizes  in  needles, 
melting  at  116°. 

Berizimido-ethyl  ether,  C6H5.C(NH)OC2H5.  The  hydrochloride 
of  this  compound  forms  large,  lustrous,  transparent  prisms, 
which  decompose  at  118° — 120°  with  formation  of  benzamide. 
In  other  respects  the  compound  resembles  its  isobutyl  analogue.1 

Benzimido-thio-ethyl  ether,  C6H5.C(NH)SC2H5.  The  hydro- 
chloride  of  this  compound  is  formed  when  hydrochloric  acid  is 
passed  into  a  mixture  of  ethyl  mercaptan  and  benzonitril : 


NH2C1 


C6H5.CN4  HS.C2H5+HC1  =  C6H5 

XSC2H5. 


It  crystallizes  in  thick  prisms,  which  melt  at   188°  and  are 
readily  soluble  in  water  and  alcohol. 

The  hydriodide  is  obtained  by  heating  thiobenzamide  to  100° 
with  ethyl  iodide  : 

NHI 


It  forms  long,  monosymmetric  prisms,  melting  at  142.°  Alkalis 
separate  the  ether  from  these  salts  as  a  strongly-smelling,  oily 
liquid,  which  is  soluble  in  water  and  readily  decomposes  into 
benzonitril  and  mercaptan.2 

1  Pinner,  Ber.  Deutsch.  Chem.  Ges.  xvi.  1654. 

2  Bernthsen,  Ann.  Chem  Pharm.  cxcvii.  348. 


202  AROMATIC  COMPOUNDS. 

Benzimido-tUobenzyl  ether,  C6H5.C(NH)S.CH2.C6H5.  The 
hydrochloride  is  obtained  by  the  action  of  benzyl  chloride  on 
thiobenzamide,  or  of  hydrochloric  acid  on  a  mixture  of  benzyl 
hydrosulphide  and  benzomtril.  It  is  soluble  in  water  and 
alcohol,  and  crystallizes  in  white  tablets  melting  at  181°.  The 
free  base  is  very  unstable  (Bernthsen). 


BENZENYLAMIDINES. 

2117  Benzenylamidine  or  Benzimido-amide,  C6H5.C(NH)NH2, 
is  formed,  as  already  mentioned,  by  the  action  of  alcoholic 
ammonia  on  the  hydrochloride  of  benzimido-isobutyl  ether  : 


HO.C4H9. 


Free  benzimido-isobutyl  ether  is  simultaneously  formed,  but 
the  quantity  of  this  product  diminishes  when  the  temperature 
at  which  the  reaction  is  carried  out  is  raised.1  The  product  is 
evaporated  in  a  vacuum,  the  residue  washed  with  ether  and 
crystallized  from  alcohol,  yielding  benzenylamidine  hydrochloride 
in  flat  needles,  which  are  decomposed  by  caustic  potash  but  not 
by  ammonia  ;  by  shaking  out  with  ether  and  evaporating,  the 
free  base  is  obtained  as  a  crystalline  mass,  which  is  slightly 
soluble  in  water,  readily  in  alcohol  and  has  an  alkaline  taste  and 
reaction.  It  decomposes  spontaneously  after  some  time  with 
evolution  of  ammonia,  which  is  also  given  off  on  heating, 
benzomtril  and  cyanphenin  being  formed. 

If  it  be  heated  to  100°  with  ethyl  iodide,  the  product 
decomposed  with  caustic  soda  and  extracted  with  ether,  ethyl- 
lenzenylamidine,  C6H5C(NC2H5)NH2,  is  obtained  as  a  strongly 
alkaline,  thick,  oily  liquid. 

Dibenzenyltriamine,  C14H13N3,  is  formed,  together  with  acet- 
amide,  when  benzenylamidine  is  boiled  with  acetic  anhydride  : 

NH 

.NH          C6H5.C^ 
2C6H5.cf  >NH  +  NH3. 


^NH 

1  Pinner  and  Klein,  Ber.  Dcutsch.  Chem.  Ges.  x.  1889. 


PHENYLBENZENYLAMIDINE.  203 

It  crystallizes  in  long,  flat  needles,  which  melt  at  108° — 109° 
and  are  not  decomposed  even  at  2400.1 

Phenylbenzenylamidine,  C6H5.C(NH)N(C6H5)H,  is  obtained, 
together  with  diphenylbenzenylamidine,  by  heating  benzouitril 

1220° — 240°  with  aniline  hydrochloride  : 
NH 
e. 
The  product  is  extracted   with  cold  water  and  the  solution 
precipitated  with  ammonia  ;  the  base  thus  obtained  is  very  readily 
soluble  in  alcohol,  and  crystallizes  badly  in  small  crusts  or  warts 
composed  of  plates,  which  melt  at  111° — 112°,  and,  on  further 
heating,  partially  sublime  and  are    partially  decomposed    into 
aniline  and  benzonitril. 

Phenylbenzenylamidine  hydrochloride  is  a  syrup,  miscible 
with  water  and  alcohol  in  all  proportions.2  It  is  converted  by 
the  action  of  sodium  amalgam  on  its  alcoholic  solution  into 
benzidenephenyldiamine,  C6H5.CH(NH2)N(C6H5)H.3 

When  phenylbenzenylamidine  is  heated  with  carbon  disul- 
phide,  its  thiocyanate  is  obtained  together  with  thiobenzanilide  ; 
an.  intermediate  product  is  probably  first  formed  and  then 
decomposed  at  the  higher  temperature :  4 


/NH\ 

^-S—^CS     =  C6H5.CS.N(C6H6)H  +  KCSH. 
\N(C6H6)H 


Symmetric  diphenylbenzenylamidine,  C6H5.C(NC6H5)N(C6H5)H. 
This  compound  was  first  prepared  by  Gerhardt,  who  obtained 
it  by  warming  benzanilide  with  phosphorus  pentachloride 
and  then  heating  the  product  with  aniline.5  The  compound 
C6H5.CC12.N(C6H5)H  is  first  formed,  and  is  converted,  with  loss 
of  hydrochloric  acid,  into  'benzanilidimidocliloride,  which  acts 
upon  the  aniline  in  the  following  manner  : 


+N(C6H6)H2  =  C6H5.C  +  HC1. 

NCI  ,  XN(C6H6)H 

1  Bcr.  Deutsch.  Chem.  Ges.  xi.  4. 

2  Bernthseu,  Ann.  Chem.  Pharm.  clxxxiv.  348. 

3  Bornthsen  and  Szymanski,  Ber.-  Deutsch.  Chem.  Ges.  xiii.  917. 

4  Bernthsen,  Ann.  Chem.  Pharm.  cxcii.  31. 

5  Ann.  Chem.  Pharm.  cviii.  217. 


204  AROMATIC  COMPOUNDS. 

Benzanilidimidochloride  crystallizes  from  petroleum  ether  in 
large,  transparent,  lustrous  plates,  melts  at  39° — 40°,  and  boils 
without  decomposition  at  about  310°;  water  decomposes  it 
rapidly,  benzanilide  being  reproduced.1 

Diphenylbenzenylamidine  is  also  formed  by  the  action  of 
aniline  on  benzenyl  trichloride,2  and  by  heating  benzanilide  with 
aniline  hydrochloride  and  phosphorus  trichloride.3  It  is  slightly 
soluble  in  water,  readily  in  alcohol,  and  crystallizes  in  needles, 
melting  at  144°  (Wallach  and  Hoffmann).  On  heating  with 
hydrochloric  acid  to  150°,  it  decomposes  into  benzoic  acid  and 
aniline,  while,  on  heating  with  sulphuric  acid,  thiobenzanilide 
and  phenyl  mustard  oil  are  formed  (Bernthsen).  Its  hydro- 
chloride,  C19H16N2.C1H,  is  only  very  slightly  soluble  in  cold 
water  and  crystallizes  from  alcohol  in  needles. 

Asymmetric  diphenylbenzenylamidine,  C6H5C(NH)N(C6H5)2,  is 
prepared  by  heating  benzonitril  with  diphenylamine  hydro- 
chloride  to  180° — 190°.  It  is  exceptionally  soluble  in  alcohol 
and  tolerably  in  ether,  from  which  it  crystallizes  in  thin,  yellowish, 
alkaline,  rhombic  tablets,  melting  at  112°.  It  decomposes  on 
boiling  into  diphenylamine  and  benzonitril ;  when  it  is  heated 
with  carbon  disulphide,  its  thiocyanate  is  formed  together  with 
diphenylthiobenzanilide,  C6H5.CS.N(C6H5)2.  Its  hydrochloride 
crystallizes  in  needles  or  monoclinic  prisms,  which  are  readily 
soluble  in  water  (Bernthsen). 

Diphenylparamidobcnzenylamidine  or  Carbotriphenyltriamine, 
C19H17N3,  was  first  prepared  by  Hofmann  by  heating  aniline 
with  tetrachloromethane ; 4  it  is  more  readily  formed,  however, 
from  tetrabromomethane.5  Weith  obtained  it  by  heating  para- 
nitrobenzoic  acid  with  aniline  and  phosphorus  trichloride,  and 
reducing  the  diphenylparanitrobenzenylamidine  thus  formed 
with  tin  and  hydrochloric  acid,6  while  Michler  and  Walder 
prepared  it  by  the  action  of  aniline  on  trichloromethylsulphonyl 
chloride,  CC13.SO2C1.7  It  is  insoluble  in  water,  slightly  soluble 
in  ether,  and  crystallizes  in  long  tablets,  melting  at  198°.  On 
distillation  it  decomposes  into  hydrocyanic  acid,  benzonitril, 
ammonia,  aniline,  and  diphenylamine,  while  on  heating  with 

1  "Wallach  and  Hoffmann,  Ann.  Chem.  Pharm.  clxxxiv.  79. 

2  Limpricht,  ibid,  cxxxv.  82  ;  Dobner,  Ber.  Deutsch.  Chem.  Ges.  xv.  233. 

3  Hofmann,  Zeitschr.  Chem.  1866,  165 

4  Hofmann,  Jahresbcr.  Chem.  1858.  351. 

5  Bolas  and  Groves,  Ann.  Chem.  Pharm.  clx.  173. 

6  Her.  Deutsch.  Chem.  Ges.  xii.  101. 

7  Ibid.  xiv.  2174. 


PHENYLENEBENZENYLAMIDINE.  205 

hydrochloric  acid  to   160°,  aniline  and  paramidobenzoic  acid  are 
formed  : 


H,N.C6H4.C  +  2F20  =  H2N.C6H,.C02H  + 

\N(C6H5)H 

2N(C6H5)H2. 

Plienyknebenzenylamidine,  C13H10N2,  was  termed  arihydro- 
lenzodiamidolenzene  by  Hiibner,  and  is  obtained  by  heating 
benzoylorthodiamidobenzene  : 

/NH2  KK. 

C6H4<  CO.C2H5  =  CflH  /        >C.C6H5  +  H20. 

XNH/  \  N  ^ 

It  may  also  be  easily  prepared  by  reducing  benzoylorthonitro- 
anilide  with  tin  and  hydrochloric  acid,  the  rise  of  temperature 
caused  by  the  reaction  being  sufficient  to  bring  about  the  forma- 
tion of  the  anhydro-base.  It  is  slightly  soluble  in  water,  readily 
in  alcohol,  and  crystallizes  from  glacial  acetic  acid  in  lustrous 
tablets,  melting  at  about  280°  ;  the  hydrochloride,  C13H10N2.C1H, 
forms  long  needles,  which  are  readily  soluble  in  water. 

The  base  is  not  attacked  by  benzoyl  chloride  even  at  260°  • 
on  heating  with  iodine  and  alcohol,  however,  the  periodide, 
C13H10N2.IH.I2,  is  formed,  and  crystallizes  in  small  plates  which 
resemble  iodine,  but  have  a  green  surface  lustre  and  are  con- 
verted by  boiling  with  water  into  the  hydriodide,  C13H10N2.IH  + 
H2O,  crystallizing  in  long,  light  yellow  needles. 

Dimethylphenylenebenzenylam.ide  ammonium  iodide,  C13H10N2 
(CH3)2I.  When  the  anhydro-base  is  heated  with  methyl  iodide 
to  180°,  the  periodide,  C13H10N2(CH3)2I3,  is  formed  ;  this  sub- 
stance crystallizes  in  long,  brownish  red  needles,  and  is  con- 
verted into  the  mono-iodide  by  boiling  in  alcoholic  solution  with 
freshly  precipitated  lead  hydroxide.  This  compound  crystallizes 
from  hot  water  in  long  needles  ;  caustic  potash  precipitates  from 
its  solution  the  hydroxide,  C13H10N2(CH3)2OH,  in  white  flocks, 
which  melt  at  152°  and  are  insoluble  in  water,  but  dissolve 
readily  in  hot  alcohol.  Its  solution  has  a  bitter  taste,  and  its 
salts  crystallize  well  ;  it  has  the  following  constitution  : 

OH 


4\      ^- 


206  AROMATIC  COMPOUNDS. 

Phenylencnitrobenzcnylwnidine,  C13H9(NO9)N9,  is  obtained  by 
dissolving  the  anhydro-base  in  fuming  nitric  acid  ;  it  crystallizes 
from  alcohol  in  yellowish,  microscopic  needles,  melting  at  196°. 
It  is  reduced  by  tin  and  hydrochloric  acid  to  amidobenzenyl- 
phtwylcne-amidine,  C13H9(NH0)N2,  which  crystallizes  from  alcohol 
in  small  needles,  melting  at  240°.  The  hydrochloride,  C13H9 
(NH2)N2(C1H)2,  forms  small  plates,  which  are  very  soluble  in 
water;  the  sulphate,  C13H9(NH2)N2.S04H2  +  2H90,  is  only 
slightly  soluble  in  hot  water,  and  crystallizes  in  broad  needles. 

A  large  number  of  other  similar  anhydro-bases  is  also 
known.1  The  following  compounds  belong  to  the  same  class. 

BenzenylamidopJienate,  C13H9NO.  Ladenburg  prepared  this 
compound  by  heating  ortho-amidophenol  with  benzoyl  chloride, 
and  by  the  distillation  of  the  former  with  phthalic  anhydride  : 


/C( 
C6H4/ 

It  crystallizes  from  dilute  alcohol  in  lustrous  plates,  melts  at 
103°,  and  boils  at  314°  —  317°  ;  it  combines  with  acids  to  form 
unstable  salts  ;  the  platinichloride,  (C13H10NO)2PtCl6,  crystal- 
lizes from  alcohol  which  contains  hydrochloric  acid  in  yellow 
prisms.  On  heating  the  base  with  concentrated  hydrochloric 
acid  to  150°,  it  decomposes  into  benzoic  acid  and  orthamido- 
phenol.2 

Benzenylamidothiophenate,  C13H9NS,  is  formed  by  boiling 
benzanilide  with  sulphur  :  3 

C6H5.CO.NH(C6H5)  +  S  =  C6H5.C^    \C6H4  +  H20. 

It  is  also  obtained  by  the  action  of  benzoyl  chloride  on  ortho- 
amidothiophenol,  as  well  as  by  heating  the  latter  with  benz- 
aldehyde,  or  benzonitril.4  It  is  formed  in  smaller  quantity, 
together  with  other  products,  when  phenyl  mustard  oil  is  heated 
with  benzoyl  chloride.5  It  crystallizes  from  alcohol  in  needles, 
which,  especially  when  heated,  smell  like  tea-roses  and 
geraniums,  melt  at  115°,  and  boil  at  about  360°.  Like  the 
preceding  compound,  it  is  a  base  and  forms  a  platinichloride 

1  Hiibner,  Ann.  Chem.  Pharm.  ccviii.  278  ;  ccix.  339  ;  ccx.  328. 

2  Ber.  Deutsch.  Chem.  Ges.  ix.  1526. 

3  Hofmann,  ibid.  xii.  2359. 

4  Ibid.  xiii.  1223.  5  Ibid.  xiii.  17. 


BENZHYDROXAMIC  ACID.  207 

which  crystallizes  in  long  needles.  It  is  not  attacked  when 
heated  with  concentrated  hydrochloric  acid  to  200°;  on  fusion 
with  caustic  potash  it  is  resolved  into  amidothiophenol  and 
benzoic  acid. 


BENZENYLOXIME   COMPOUNDS. 

2118  The  three  hydrogen  atoms  of  hydroxylamine  can,  as  was 
pointed  out  by  Lossen,  be  successively  replaced  by  benzoyl  : 

Benzhydroxylamine,  NOH2(CO.C6H5), 
Dibenzhydroxylamine,  NOH(CO.C6H5)2, 
Tribenzhydroxylamine,  NO(CO.C6H5)3. 

The  last  of  these  compounds  is  an  indifferent  substance  ;  the 
two  others  are  acids,  and  have  therefore  been  called  by  Lossen 
benzhydroxamic  acid  and  dibenzhydroxamic  acid.1  Certain 
cases  of  physical  isomerism  and  of  metamerism  are  characteristic 
of  them  and  their  derivatives.  Lossen  showed  somewhat  later 
that  these  peculiarities  as  well  as  numerous  decompositions  of  the 
compounds  in  question  can  readily  be  explained  if  benzhydrox- 
amic acid  be  looked  upon  as  an  oximido-compound  of  benzenyl  ;2 
its  formation  is  then  expressed  by  the  following  equations: 

N.OH 
C6H5.COC1  +  H2N.OH  =  C6H5.C  +  HO. 


/N.OH  /N.OH 

C,H6.CC  +  H20  =  C6H5.Cf  4-  HC1. 

\C1  \OH 

It  is,  however,  also  possible  that  the  hydroxylamine  forms  an 
additive  compound  with  the  benzoyl  chloride,  and  that  hydro- 
chloric acid  is  then  given  off  :  3 


-OH  /OH 

VNH.OH  -  C6H5.C/ 

\ci 


C6H5.CNH.OH  =  CH.C<  +  HC1. 


1  Ann.  Chem.  Pharm.  clxi.  347. 

2  Ber.  Deutsch.  Chem.  Ges.  xvi.  873. 

3  Ibid,  xviii.  1189. 


208  AROMATIC  -COMPOUNDS. 

The  other  compounds  are  then  formed  by  the  replacement  of 
the  hydrogen  of  the  hydroxyls. 

Hydroxylamine  hydrochloride  is  dissolved  in  8 — 10  parts 
of  water,  together  with  an  equivalent  amount  of  sodium  car- 
bonate, and  3  parts  of  benzoyl  chloride  gradually  added,  the 
whole  being  then  well  shaken  up  and  cooled;  the  dibenz- 
hydroxamic  acid  separates  out  together  with  a  portion  of  the 
benzhydroxamic  acid,  which  is  removed  by  recrystallization 
from  hot  alcohol.  The  benzhydroxamic  acid  remaining  in  the 
solution  is  precipitated  by  barium  chloride,  and  then  liberated 
from  the  well-washed  precipitate  by  dilute  sulphuric  acid.  A 
further  quantity  of  it  can  be  obtained,  since  dibenzhydroxamic 
acid  splits  up  into  benzoic  acid  and  benzhydroxamic  acid  when 
heated  with  baryta  water. 

Benzhydroxamic  acid  or  Benzenyloximic  acid,  C6H5.C(OH)NOH, 
crystallizes  in  rhombic  plates  or  tablets,  and  dissolves  in  44*5 
parts  of  water  at  6°,  much  more  readily  in  tolerably  warm  water, 
very  readily  in  alcohol  and  slightly  in  ether.  It  has  an  acid 
reaction,  melts  at  124° — 125°,  and  undergoes  a  sudden,  violent 
decomposition  at  a  higher  temperature.  When  heated  with  dilute 
hydrochloric  acid,  it  decomposes  into  hydroxylamine  and  benzoic 
acid.  It  is  monobasic,  but  forms  acid  salts  with  the  alkali  metals. 

Acid  potassium  benzhydroxamate,  C6H5.C(OH)NOK-f  C6H3.C 
(OH)NOH,  is  tolerably  soluble  in  cold  water,  scarcely  in  alcohol, 
and  crystallizes  in  small  rhombic  plates  or  flat,  pointed  prisms, 
which  deflagrate  sometimes  with  the  production  of  flame,  when 
heated.  The  normal  salt  is  readily  soluble  in  alcohol ;  on 
evaporation  of  the  solution,  however,  the  acid  salt  and  potassium 
carbonate  separate  out. 

Acid  sodium  benzhydroxamate,  C6H5.C(OH)NOjSTa-f-C6H5.C 
(OH)NOH  +  3H20,  is  somewhat  more  readily  soluble  in  water, 
slightly  in  alcohol,  and  crystallizes  in  long,  thin  plates,  or  large 
elongated  tablets,  which  rapidly  deliquesce  in  the  air. 

Acid  barium  hydroxamate,  (C7H6NO2)2Ba  +  C7H7NO2,  forms 
small  prisms  scarcely  soluble  in  water  and  alcohol. 

Normal  barium  hydroxamate,  (C7H6NO2)2Ba,  is  obtained  by 
the  addition  of  barium  chloride  to  a  solution  of  the  acid 
potassium  salt  which  has  been  treated  with  ammonia ;  it  forms 
microscopic  needles.  The  calcium  salt  is  a  precipitate  resembling 
alumina ;  the  benzhydroxamates  of  most  of  the  other  metals  are 
also  insoluble. 

The  behaviour  of  the  acid  and  its  acid  salts  towards  ferric 


DIBENZHYDROXAMIC  ACID.  209 

chloride  is  very  characteristic  ;  a  dark  red  precipitate  is  formed 
which  dissolves  in  an  excess  of  the  precipitant  with  a  deep 
cherry-red  colour,  which  is  not  altered  by  the  addition  of  dilute 
hydrochloric  or  sulphuric  acid,  but  is  destroyed  by  concentrated 
hydrochloric  acid  ;  the  addition  of  water  causes  the  reappearance 
of  the  colour.  If  the  original  solution  contains  hydrochloric 
acid,  ferric  chloride  only  produces  a  colouration. 

When  the  barium  salt  is  distilled  with  a  little  water  aniline  is 
formed : l 

2(C0H6C(OH)NO)2Ba  +  H20  =  2C6H5.NH2  +  C02+BaC03. 

Ethyl  benzhydroxam-ate,  C6H5.C(OH)OC2H5,  is  obtained  by  the 
action  of  ethyl  iodide  and  caustic  potash  on  a  solution  of  the 
acid  in  alcohol,2  as  well  as  by  that  of  benzoyl  chloride  on  ethyl 
hydroxylamine,  H2N(OC2H5).3  It  is  very  slightly  soluble  in 
water,  readily  in  alcohol,  and  crystallizes  in  thick  tablets,  which 
melt  at  64° — 65°  and  are  resolved  at  190°  into  alcohol,  aldehyde, 
benzamide  and  phenyl  isocyanate.  It  is  readily  soluble  in 
alkalis,  being  re-precipitated  from  solution  by  acids  and  even  by 
carbon  dioxide ;  on  heating  with  concentrated  hydrochloric  acid, 
it  decomposes  into  benzoic  acid  and  ethyl  hydroxylamine.  If 
equal  molecules  of  the  ether  and  caustic  potash  be  dissolved  in 
alcohol  and  treated  with  silver  nitrate,  a  white  precipitate 
of  C6H5.C(OAg)NOC2H5,  is  obtained,  which  blackens  only  on 
heating,  while  silver  benzhydroxamate  blackens  and  decomposes 
immediately  on  precipitation. 

Benzoyl  ethylbenzhydroxamate,  or  Benzethylbenzhydroxylamine, 
C6H5.C(O.CO.C6H5)NOC2H5,  is  obtained  by  the  action  of  benzoyl 
chloride  on  an  alkaline  solution  of  the  ether ;  it  is  readily  soluble 
in  alcohol  and  ether  and  forms  transparent  rhombic  crystals, 
melting  at  48°— 49°.4 

2119  Dibenzhydroxamic  acid,  or  Benzoylbenzoximic  acid,  C6H5.C 
(OH)NO.CO.C6H5,  which  is  produced  by  the  action  of  benzoyl 
chloride  on  benzhydroxamic  acid,  crystallizes  from  hot  alcohol  in 
needles,  and  on  the  spontaneous  evaporation  of  the  solution  in 
large,  lustrous,  rhombic  prisms  ;  it  has  an  acid  reaction,  melts  at 
1530,5  and  decomposes  violently  at  a  higher  temperature  with 
formation  of  carbon  dioxide,  benzoic  acid,  benzanilide  and  phenyl 
isocyanate.6  On  heating  with  hydrochloric  acid  it  splits  up  into 

1  Ann.  Chem.  Pharm.  clxxv.  323.  2  Waldstein,  ibid,  clxxxi.  384. 

8  Giirke,  ibid.  ccv.  278.  4  Pieper,  ibid,  ccxvii.  8. 

5  Steinor,  ibid,  clxxviii.  226.  6  Pieschel,  ibid,  clxxv.  305. 


210  AROMATIC  COMPOUNDS. 

benzole  acid  and  hydroxylamine,  while  alkalis  decompose  it  into 
benzhydroxamic  acid  and  benzoic  acid,  so  that  the  former  acid 
can  be  prepared  from  it  by  means  of  baryta  water.  Its  alkali 
salts  on  the  other  hand  are  decomposed  by  water  even  in  the  cold, 
more  rapidly  on  heating,  with  formation  of  benzoic  acid,  carbon 
dioxide  and  diphenyl  urea  : 


NO.CO.C6H6 

2C6H5.Cf  +  H20  =  2C6H6.CO.OK 

\OK 

/N(C6H5)H 
C0(  +  CO,. 

\N(C6H5)H 


As  already  mentioned,  benzhydroxamic  acid  can  be  directly 
converted  into  aniline,  while  dibenzhydroxamic  acid  yields 
derivatives  of  this — phenyl  isocyanate,  benzanilide  and  diphenyl 
urea — from  which  aniline  can  easily  be  obtained.  Since  the 
homologues  of  benzoic  acid  also  yield  oximes,  a  general  method 
is  established  by  which  the  carboxyl  of  a  monobasic  aromatic 
acid  can  be  replaced  by  an  amido-group  (Lossen). 

Inversely,  the  amido-group  of  amido-compounds  can  be  re- 
placed by  carboxyl,  and  aniline  thus  converted  into  benzoic  acid 
(Part  III.  p.  31). 

Potassium  dibenzhydroxamate,  C6H5.C(OK)NO.CO.C6H5,  is 
precipitated  in  thin  plates  when  alcoholic  solutions  of  the  acid 
and  caustic  potash  are  mixed.  If  silver  nitrate  be  added  to  its 
freshly  prepared  aqueous  solution,  a  white  precipitate  of  the 
silver  salt  is  obtained  ;  if  this  be  dried,  covered  with  ether  and 
treated  with  ethyl  iodide,  the  ethyl  ether  is  obtained  in  two 
isomeric  forms,  one  of  which  is  an  oily  substance,1  while  the 
other  is  dimorphous. 

a-Ethyl  dibemhydroxamate,  C6H5.C(OC2H5)NO.CO.C6H5,  is 
the  chief  product  of  the  reaction ;  it  is  readily  soluble  in  ether 
and  alcohol,  and  crystallizes  In  four-  or  eight-sided  rhombic 
prisms,  melting  at  58.° 

ft-Ethyl  dibcnzhydroxamate,  which  is  only  formed  in  very  small 
quantity,  is  more  readily  soluble  than  the  a-compound  and  forms 
triclinic  crystals,  melting  at  63°. 

These  modifications  cannot  be  directly  converted  into  each 

1  Eiseler,  Ann.  Chcm.  Pharm.  clxxv.  326  ;  Giirke,  ibid.  ccv.  279. 


TiUBENZHYDROXYLAMINE.  211 

other;  on  heating  they 'decompose  into  benzonitril,  aldehyde  and 
ben  zoic  acid  : 

C6H5.C(OC2H5)NO.CO.C6H5  =  C6H5.CN  +  C2H4O+ 
C6H5CO.OH. 

Concentrated  hydrochloric  acid  decomposes  them  into  benzoic 
acid,  ethyl  benzoate  and  hydroxylamine,  while  on  heating  with 
caustic  potash,  benzoic  acid  and  two  isomeric  ethylhydroxamic 
acids  are  formed. 

The  oily  ether  is  also  readily  soluble  in  alcohol  and  ether, 
and  behaves  chemically  like  the  two  others  ;  it  is  only  formed  in 
small  quantity  and  has  not  been  closely  investigated. 

a-Ethylbenzhydroxamic  acid,  C6H5.C(OC2H5)NOH,  is  readily 
soluble  in  alcohol  and  ether ;  it  crystallizes  from  a  mixture  of 
ether  and  benzene  in  monoclinic  tablets  or  prisms,  melting  at  53'5°. 

The  ethyl  ether,  C6H5.C(OC2H5)NOC2H5,  is  formed  by  the 
action  of  ethyl  iodide  on  a  solution  of  the  acid  in  alcoholic 
potash.1  It  is  a  powerfully  refractive  liquid  which  has  a 
pleasant  aromatic  odour,  and  boils  at  244°  with  slight  decom- 
position ;  its  vapour  has  a  sp.  gr.  of  6 '5 6  (Giirke).  On  heating 
with  alcohol  and  hydrochloric  acid,  it  forms  ethyl  benzoate 
and  ethyl  hydroxylamine. 

fB-Ethylhydroxamic  acid  is  isomorphous  with  the  a-compound, 
but  it  melts  at  67'5° — 68°,  is  more  soluble  in  petroleum  spirit, 
less  so  in  caustic  potash,  and  is  more  readily  extracted  from 
this  by  ether.  Its  ethyl  ether  is  so  similar  to  that  of  the 
a-compound  that  it  is  doubtful  whether  they  are  distinct 
substances. 

Both  acids  are  formed  simultaneously  by  the  action  of 
hydroxylamine  on  benzimido-ethyl  ether.2 

It  is  almost  completely  converted  into  ethyl  /3-dibenzhydroxa- 
mate  by  the  action  of  benzoyl  chloride.3 

'2 1 20  Tribenzhydro&ylamine,  or  Dibcnzobenzoximate,  C6H5.C 
(O.CO.C6H5)NO.CO.C6H5,  is  obtained  in  three  modifications  by 
treating  dry  hydroxylamine  hydrochloride  with  a  solution  of 
benzoyl  chloride  in  toluene,  or  by  heating  potassium  dibenz- 
hydroxamate  with  benzoyl  chloride.4  It  is,  however,  best 

1  Lessen  and  Zarmi,  Ann.  Chem.  Pharm.  clxxxii.  220. 

2  Lessen,  Bcr.  Deutsch.  Chem.  Ges.  xvii.  1587. 

3  Giirke,  Ann.  Chem.  Pharm.  ccv.  281. 

4  Lessen,  Ann.   Chem.  Pharm.   clxi.  360  ;  clxxv.   282  ;  clxxxvi.   34  ;  Steiner, 
ibid,  clxxviii.  225. 


212  AROMATIC  COMPOUNDS. 

prepared  by  acting  upon  silver  dibenzhydroxamate  with  a  solution 
of  benzoyl  chloride  in  petroleum  ether,  and  allowing  the  whole 
to  stand  until  the  silver  chloride  has  separated  as  a  dense 
precipitate  (Lossen). 

a-Tribenzhydroxylamine  is  slightly  soluble  in  cold,  more 
readily  in  hot  alcohol  and  ether,  and  forms  monoclinic  crystals, 
elongated  in  the  direction  of  the  ortho-diagonal,1  which  melt  at 
100°.  It  is  completely  split  up  into  benzoic  acid  and  dibenz- 
hydroxamic  acid  by  heating  for  an  hour  with  hydrochloric  acid 
of  sp.  gr.  1*05. 

p-Tribcnzhydroxylamine  is  insoluble  in  ether,  slightly  soluble 
in  cold,  more  readily  in  hot  alcohol,  and  forms  small,  lustrous, 
monoclinic  crystals,  melting  at  141° — 142°  (Klein  and  Trech- 
mann).  It  is  decomposed  by  concentrated  hydrochloric  acid  at 
150°  into  benzoic  acid,  dibenzhydroxamic  acid  and  hydroxyl- 
amine. 

<y-Tribenzhydroxylamine  is  only  formed  in  small  quantity;  it 
crystallizes  in  short,  monoclinic  prisms,  melting  at  112°,  and  is 
to  a  large  extent  converted  into  the  /3-cOmpound  by  dilute 
hydrochloric  acid. 

All  the  three  modifications  are  resolved  on  dry  distillation 
into  benzoic  anhydride  and  phenyl  isocyanate  : 

,NO.COC6H5 

C6H5.C<;  '  =  C6H5NCO+(CO.C6H5)20. 

\O.CO.C6H5 

They  are  decomposed  by  alcoholic  potash  into  dibenzhydrox- 
amic acid  and  benzoic  acid. 

The  chemical  behaviour  of  these  substances  is  therefore  iden- 
tical, and  they  present  an  instance  of  trimorphism,  for  although 
they  all  crystallize  in  forms  belonging  to  the  monoclinic  system, 
these  forms  are  distinct  ones  and  cannot  be  derived  from  one 
another. 

Benzenylamidoxime,  or  Benzhydroxamide,  C6H5.C(NOH)NH2, 
is  formed  when  a  solution  of  hydroxylamine  and  benzonitril  in 
dilute  alcohol  is  heated  to  80°  for  about  eighteen  hours : 2 

_N.OH 
C6H5.C=N  +  H2N.  OH  =  C6H5.C7~ 

XNH2. 

1  Klein  and  Trechmann,  Ann.  Chem.  Pharm.  clxxxvi.  104. 

2  Kriiger  and  Tiemann,  Ber.   Dcutsch.  Chem.  Ges.  xvii.  126,  1687  ;  xviii.  727, 
1053. 


BENZHYDROXAMIDE.  213 

It  is  also  formed  by  the  action  of  hydroxylamine  on  benz- 
amidine,  C6H5.C(NH)NH2,  and  was  described  by  Pinner  as 
benzoxamidine.1 

It  is  readily  soluble  in  alcohol  and  ether,  and  crystallizes  from 
hot  water  in  long,  flat,  acute  prisms,  melting  at  79°  —  80°.  It  is 
precipitated  by  petroleum  spirit  from  its  solution  in  benzene  in 
needles.  Its  solution  is  coloured  deep  red  by  ferric  chloride  ;  it 
forms  salts  both  with  acids  and  bases.  Benzamide  and  nitrous 
oxide  are  formed  by  the  action  of  sodium  nitrite  on  its  hydro  - 
chloride,  while  when  heated  to  200°  with  hydrochloric  acid,  it 
decomposes  into  ammonium  chloride  and  benzoic  acid. 

Benzenylamidoxime  is  poisonous  ;  thus,  0'5  grm.  proved  fatal 
to  a  dog,  O'l  grm.  to  a  rabbit,  and  0'Q3  grm.  to  a  frog. 

Its  alkyl  ethers  are  formed  by  heating  the  sodium  salt  with 
the  corresponding  iodide. 

Ethyl  ether  of  lenzenylamidoxime,  C6H5.C(NOC2H5)NH2,  is 
almost  insoluble  in  water,  but  readily  soluble  in  alcohol  and 
ether,  and  crystallizes  in  rhombic  plates,  which  melt  at  67°,  and 
dissolve  in  acids  but  not  in  alkalis.  Its  hydrochloride  crystal- 
lizes well. 

Benzcnylethoxime  chloride,  C6H5.C(NOC2H5)C1,  is  formed  when 
sodium  nitrite  is  added  to  a  well-cooled  solution  of  the  ether  : 


C6H5.C(NOC2H5)NH0  +  HC1  +  NaNO2  =  C6H5.C(NOC2H5)OH 

+  NaCl  +  H20  +  Ng. 

C6H6.C(NOC2H5)OH  +  HC1  =  C6H5(NOC2H5)C1  +  H2O. 

According  to  Lossen,  a  diazo-compound  is  probably  formed  at 
first,  and  then  decomposes  in  the  following  mariner  :  2 


X>NOC2H5 

c6H5.c<;  +  HOI  =  c6H5.c  r          +  N2  -h  H2o. 

\C1 


The  chloride  is  also  readily  produced  by  the  action  of  phosphorus 
mtachloride  on  ethyl  benzhydroxamate,  C6H5.C(NOC2H5)OH.3 
It  is  an  oily,  aromatic  liquid,  which  boils  at  239°,  is  not  decom- 
posed by  water  or  alcohol,  and  is  not  even  attacked  when  heated 
for  a  short  time  with  acids  and  alkalis.  When  heated  with 
Icoholic  ammonia  to  160°  —  180°,  however,  the  amidoxime  ethyl 
jther  is  re-formed,  and  it  is  converted  by  the  action  of  a 

1  Kriiger  and  Ticmann,  Ber  Deutsch.  Chem.  Ges.  xviii.  184. 

2  Ber.  Deutsch.  Chem.  Ges.  xviii.  1193.  3  Ibid. 

245 


214  AROMATIC  COMPOUNDS. 

solution  of  sodium  in  absolute  alcohol  into  ethyl  ethylbenz- 
hydroxamate. 

Benzoylbenzenylamidoxime,  C6H5.C(NO.CO.C6H5)NH2,  is 
formed  by  the  action  of  benzoyl  chloride  on  benzenylamidoxime. 
It  crystallizes  in  fine,  white  needles,  which  melt  at  140°,  and 
are  soluble  in  alcohol,  ether,  and  acids,  but  not  in  alkalis. 

2  121  Dibcnzenylazoxime,  (C7H5)2N2O,  is  obtained  by  heating 
the  compound  just  described  beyond  its  melting-point,  or  by 
treating  it  with  dehydrating  agents,  such  as  benzoic  anhydride 
or  benzoyl  chloride  : 

NO.CO.C6H5  NO, 

C6H,C^  =  C6H,C^        \C.C,H,  +  H/>. 

\NH2  X-N-^ 

It  is  scarcely  soluble  in  water,  but  readily  in  alcohol,  and 
crystallizes  in  long,  fine  needles,  which,  after  drying,  resemble 
asbestos  and  melt  at  108°,  but  sublime  at  a  much  lower 
temperature. 

Ethenylbenzenylazoxime  is  formed  by  the  action  of  acetic  anhy- 
dride on  benzenylamidoxime,  and  is  very  similar  to  the  preceding 
compound,  crystallizing  in  needles  which  readily  sublime,  have  a 
characteristic  odour  and  melt  at  41°.  It  is  isomeric  with  benz- 
enylethenylazoxime,  which  is  obtained  by  the  action  of  benzoyl 
chloride  on  ethenylamidoxime,  CH3.C(NOH)~NH2,  and  forms 
aromatic  needles,  which  melt  at  57°  and  sublime  very  easily.1 
The  isomerism  of  these  two  compounds  is  shown  by  the  follow- 
ing formulae  : 

Ethenylbenzenylazoxime.  Benzenylethenylazoxime. 


C.CH3  3.  . 


Acetylbenzenylamidoxime,  C6H5.C(NO.CO.CH3)NH2,  is  formed 
by  the  action  of  acetyl  chloride  on  an  ethereal  solution  of  benz- 
enylamidoxime. It  crystallizes  from  alcohol  in  small  plates  or 
flat  prisms,  which  melt  at  96°,  and  are  easily  converted  into 
ethenylbenzenylazoxime,  the  change  being  brought  about  even 
by  boiling  with  water.2 
Ethyl  benzenylamidoximecarboxylate,  C6H5.C(NH2)NO.CO.OC2H6, 

1  Nordmann,  Ber.  Deutsch.  Chem.  Ges.  xv.  2754. 

2  Schultz,  ibid,  xviii.  1080. 


BENZENYLAZOXIME  CARBINOL.  215 

is  obtained  by  adding  ethyl  chlorocarbonate  to  a  solution  of 
benzenylamidoxime  in  chloroform.  It  crystallizes  in  long, 
lustrous  needles,  which  melt  at  127°  and  are  decomposed  at  a 
higher  temperature,  or  on  heating  with  water,  into  the  following 
compound,  alcohol  being  removed  : 

Benzenylazoxime  carbinol,  C8H6N2O2,  is  most  simply  prepared 
by  heating  benzenylamidoxime  with  ethyl  chlorocarbonate.  It 
crystallizes  from  hot  water  in  long  needles/melting  at  197°. 
It  readily  dissolves  in  alkalis  ;  its  aqueous  solution  has  an  acid 
reaction  and  decomposes  the  carbonates  of  the  alkaline  earth 
metals.  Silver  nitrate  precipitates  the  white  crystalline  silver 
salt  from  a  solution  neutralized  with  ammonia,  and  copper  sul- 
phate, the  green  copper  salt,  (C8H5N202)2Cu. 

According  to  the  method  by  which  it  is  prepared,  benzenyl-, 
azoxime  carbinol  should  have  the  first  of  the  following  formulse  ; 
its  whole  behaviour,  however,  corresponds  with  the  second,  and 
an  intramolecular  change  must  therefore  be  assumed  : 


Carbonyldibenzenylamidoxime,  (C6H5.C  (NH2)NO)2CO,  is  formed 
when  benzenylamidoxime  is  brought  into  contact  with  carbonyl 
chloride  dissolved  in  benzene.  It  is  almost  insoluble  in  the 
latter  and  is  precipitated  by  water  from  its  alcoholic  solution 
in  small  plates,  melting  at  128°  —  129°.  On  heating  with 
caustic  soda  solution,  the  preceding  compound  is  formed.1 

Benzenylazoxime  propenylcarloxylic  acid,  C11HION2O3,  is  ob- 
tained by  heating  benzenylamidoxime  with  succinic  andydride  : 

CH2-COV 
+  |  \0  =  . 

CH2—  CCK 

N—  (X 
C6H5-C\  J)C—  CH2—  CH2—  CO.OH  -f  H2O. 

It  crystallizes  from  hot  water  in  small,  lustrous,  white,  rhombic 
plates  or  prisms,  melting  at  1  20°. 

The  anhydrides  of  other  dibasic  acids  give  similar  compounds.2 

1  Falck,  Ber.  Deutsch.  Chem.  Oes.  xviii.  2467. 

2  Schultz,  ibid,  xviii.  2458. 


216  AROMATIC  COMPOUNDS. 

Metanitrobenzcnylamidoximc,  C6H4(NO2)C(NH2)NOH.  Meta- 
nitrobenzonitril  readily  combines  with  hydroxylamine  to  form 
this  compound.  It  crystallizes  in  orange -coloured  prisms,  melt- 
ing at  174°.  A  series  of  compounds  has  been  prepared  from  it, 
corresponding  to  those  described  above.1 

Mctamidobenzenylamidoxime,  C6H4(NH2)C(NH2)NOH,  is 
formed  by  the  reduction  of  the  preceding  compound,  and 
separates  from  ether  as  a  yellow  oil  which  gradually  solidifies. 
Its  hydrochloride,  C6H4(NH3C1)C(NH3C1)NOH,  crystallizes 
from  hot  water  in  prisms. 

Metahydroxylenzenylamidoxime,  C6H4(OH)C(NH2)NOH,  has 
been  prepared  from  the  amido-compound  by  the  diazo-reaction, 
and  crystallizes  from  dilute  alcohol  in  light  yellow  needles,  melt- 
ing at  1630.2 


HALOGEN-SUBSTITUTION    PRODUCTS    OF 
BENZOIC    ACID. 

2122  When  an  atom  of  hydrogen  in  benzoic  acid  is  replaced 
by  an  element  of  the  chlorine  group,  a  meta-compound  is  formed, 
and  not,  as  in  the  case  of  toluene  and  the  benzyl  compounds,  a 
para-compound,  accompanied  by  a  small  amount  of  an  ortho- 
compound. 

Substituted  benzoic  acids  are  obtained  by  the  oxidation  of  the 
corresponding  alcohols  and  aldehydes,  as  well  as  of  the  substitu- 
tion products  of  toluene  and  such  other  compounds  as  are  them- 
selves readily  oxidized  to  benzoic  acid. 

They  may  also  be  obtained  from  the  amidobenzoic  acids  by 
means  of  the  diazo-reaction.  The  old  method,  proposed  by 
Griess,  consisted  in  heating  a  diazo- amidobenzoic  acid  with 
hydrochloric,  hydrobromic,  or  hydrofluoric  acid  : 

N.NH.C6H4.C(XH 

1 1  -+  HC1  =  NH2.C6H4.CO2H  +  C6H4C1.CO0H  +  N2. 

NC6H4.C02H 

He  subsequently  found  that  the  sulphates  of  the  diazobenzoic 
acids  are  more  suitable  for  the  purpose  ;  one  part  is  boiled 
with  3  to  5  parts  of  the  hydracid,  the  substituted  benzoic  acid 

1  Schopff,  Ber.  Dcutsch.  Chem.  Ges.  xviii.  1063.          2  lUd.  xviii.  2472. 


ORTHOCHLOROBENZOIC  ACID.  217 


separating  out  on  cooling  as  a   mass  of  crystals.      Hydriodic 
acid  acts  in  this  way  even  in  the  cold : * 


NC6H4.C02H 

+  HI  =  C6H4LC02H  +  S04H2  +  N2. 
•H 


NS04] 


A  reaction  which  possesses  considerable  theoretical  interest 
has  been  employed  for  the  preparation  of  these  compounds  by  v. 
Richter.  When  paranitrochlorobenzeneorparanitrobromobenzene 
is  heated  with  alcohol  and  potassium  cyanide,  the  nitroxyl  group 
is  replaced  by  hydrogen,  and  the  cyanogen  group  takes  the 
meta-position,  the  nitnl  of  metachloro-  or  metabromobenzoic 
acid  being  formed,  while  metanitrochlorobenzene  is  converted 
into  orthochlorobenzoyl  chloride.  Orthonitrochlorobenzene  and 
orthonitrobromobenzene,  on  the  other  hand,  are  not  attacked  by 
potassium  cyanide.2 

The  halogen-substitution  products  are  readily  converted  into 
benzoic  acid  by  the  action  of  sodium  amalgam  and  water. 


MONOCHLOROBENZOIC  ACIDS,  C6H4C1.CO2H. 

2122  Orthochlorobenzoic  acid  was  obtained  by  Chiozzain  1852, 
by  heating  salicylic  acid  (orthohydroxybenzoic  acid)  with  phos- 
phorus pentachloride,  and  decomposing  the  fraction  of  the  dis- 
tillate boiling  between  200° — 250°  with  water.3  It  was  believed 
to  be  identical  with  the  chlorobenzoic  acid  which  is  formed  by 
the  direct  chlorination  of  benzoic  acid,  until  Limpricht  and  Uslar, 
as  well  as  Kolbe  and  Lautemann,  showed  that  the  latter  compound 
is  a  distinct  substance,  and  gave  it  a  distinctive  name,  chloro- 
salylic  acid.4  Kekule  obtained  the  same  acid  in  a  similar 
manner  from  wintergreen  oil,  which  consists  chiefly  of  methyl 
salicylate.5 

Its  formation  will  be  discussed  under  salicylic  acid.  In  order 
to  prepare  it,  an  intimate  mixture  of  one  molecule  of  sodium 
salicylate  with  two  molecules  of  phosphorus  pentachloride  is 
distilled,  the  portion  boiling  above  240°  separated,  and  de- 
composed by  boiling  caustic  soda  solution,  the  acid  being  then 
precipitated  by  hydrochloric  acid  (Kolbe  and  Lautemann). 
The  precipitate  is  dissolved  in  the  smallest  possible  quantity  of 

1  Bcr.  Deutsch.  Chem.  Gen.  xviii.  960.  3  Ibid.  iv.  459. 

3  Ann.  Chem.  Pharm  Ixxxiii.  317.         *  Ibid.  cxv.  183.         9  Ibid,  cxvii.  145. 


21-8  AROMATIC  COMPOUNDS. 

boiling  water  arid  treated  with  a  slight  excess  of  weak  milk  of 
lime ;  calcium  salicylate  is  thus  formed  and  separates  completely 
when  the  solution  is  well  stirred  and  heated  on  the  water-bath 
for  some  hours.  The  filtrate  is  precipitated  with  hydrochloric 
acid,  and  the  orthoehlorobenzoic  acid  purified  by  re-crystallization 
from  boiling  water.1  The  mixture  of  acids  can  also  be  separated 
.by  distillation  with  steam,  with  which  salicylic  acid  alone  vola- 
tilizes.2 

Pure  salicylic  acid  may  be  substituted  for  the  sodium  salicylate.3 
According  to  Glutz,  it  is  better  to  employ  wintergreen  oil,  to 
which  the  phosphorus  pentachloride  must  be  gradually  added, 
the  mixture  heated  for  a  considerable  time  until  hydrochloric 
jacid  ceases  to  be  evolved,  and  then  distilled  and  treated  as 
.above.4 

Orthoehlorobenzoic  acid  is  also  formed  when  orthochloro- 
toluene  is  boiled  with  a  dilute  solution  of  potassium  perman- 
ganate.5 It  dissolves  in  881  parts  of  water  at  0°,  is  readily 
soluble  in  hot  water  and  alcohol,  and  crystallizes  in  long,  silky 
needles,  which  melt  at  137°,  and  sublime  in  lustrous  crystals. 
It  melts  when  heated  with  a  little  water,  in  the  same  manner  as 
benzoic  acid.  ,WJien  heated  to  200°  with  caustic  potash,  it 
yields  10  per  cent,  of  salicylic  acid  and  20  per  cent,  of  meta- 
hydroxybenzoie  acid,  equal  quantities  being  formed  when  caustic 
soda  is  employed  (Ost). 

Calcium  wthocblorobenzoate,  (C7H4C102)2Ca  +  2H2O,  crystallizes 
in  prisms,  which  are  Very  slightly  soluble  in  alcohol,  but  very 
readily  in  water.  The  solution  of  the  acid  in  ammonia  is  there- 
fore not  precipitated  by  calcium  chloride,  and  it  may  thus  be 
distinguished  from  its  isomerides. 

Orthochlorobenzoyl  chloride,  C6H4C1.COC1,  is  obtained  in  the 
pure  state  by  the  action  of  phosphorus  chloride  on  the  acid.  It 
is  a  heavy,  powerfully  refractive  liquid  which  fumes  in  the  air 
and  boils  at  235°— 238°  (Emmerling). 

OrtJiochlorobenzonitril,  C6H4C1.CN,  is  formed  by  the  action  of 
phosphorus  pentachloride  on  salicylamide,  C6H4(OH)CO.NH2, 
It  crystallizes  from  hot  water  or  ether  in  white  needles,  which 
-smell  like  benzonitril  and  melt  at  42° — 43°.  It  sublimes  readily, 

,    *  Beilstein  and  Reiqhenbach,  Ann.  Chem.  Pharm.  cxxxii.  311. 

*  Hiibner  and  Upmann,  Zcitschr.  Ckcm.  1870,  293. 

'  •  3  Hiibner  and  Biedermann,  Ann.    Chcm.   Pharm.   cxlii.    263  ;    Wilkens  and 
Rack,  ibid,  ccxxii.  192. 

4  Glutz,  ibid,  exliii.  194  ;  Ost,  Journ.  Pratt.' Chcm.  [2]  ad.  386, 

5  Emmerling,  Ber.  Deutsch.  Chcm.  Ges.  viii.,880. 


METACHLOROBENZOIC  ACID.  219 

boils  at  232°,  and  is  converted  into  orthochlorobenzoic  acid  when 
heated  to  150°  with  dilute  hydrochloric  acid.1 

2124  Metaclilorobenzoic  acid.  Herzog,  in  1840,  found  that  the 
action  of  chlorine  upon  benzoic  acid  produces,  among  other  pro- 
ducts, a  chlorinated  acid  resembling  benzoic  acid,  but  he  did  not 
analyze  the  substance.2  Scharling  subsequently  obtained  an  acid 
by  the  distillation  of  urine  with  hydrochloric  acid,  which  had  the 
composition  of  chlorobenzoic  acid,  and  which  he  named  chloro- 
michmic  acid  (o/jLt^a,  urine),3  but,  as  Gmelin  pointed  out,  it 
was  not  to  be  distinguished  from  chlorobenzoic  acid.4  Stenhouse 
prepared  the  latter  by  treating  benzoic  or  cinnamic  acid  with 
chlorine,  bleaching  powder  or  potassium  chlorate  and  hydro- 
chloric acid,  but  was  unable  to  free  it  from  higher  chlorine 
substitution  products.5  Field,  however,  found  that  it  can  be 
obtained  pure  by  boiling  benzoic  acid  with  potassium  chlorate 
and  hydrochloric  acid,  and  this  was  confirmed  by  Otto.6  As 
already  mentioned,  this  acid  was  believed  to  be  identical  with 
the  chlorobenzoic  acid  prepared  from  salicylic  acid,  until  Lim- 
pricht  and  Uslar  showed  that  the  acid  obtained  in  this  way  is 
different  from  that  obtained  by  treating  sulphobenzoic  acid  with 
phosphorus  pentachloride,  and  decomposing  the  resulting  chloro- 
benzoyl  chloride  with  water.7  The  chlorobenzoic  acids  formed 
by  these  different  reactions  were  made  the  subject  of  a  close 
investigation  by  Beilstein  and  Schlun,  which  resulted  in  their 
proving  the  existence  of  three  isomerides,  the  third  of  which 
had  been  obtained  by  Beilstein  and  Wilbrand  from  iiitrodracylic 
acid  (Part  III.  p.  34).8 

Metachlorobenzoic  acid  was  also  obtained  by  Saint-Evre 9 
by  the  action  of  chlorine  on  a  solution  of  benzoic  acid  in  caustic 
potash,  and  was  named  chloronicelnic  acid,  C6H5C102.  It.  is 
also  formed  when  benzoic  acid  is  heated  with  antimony  chloride 
and  the  product  treated  with  water,10  as  well  as  by  the  oxidation 
of  metachlorotoluene  with  chromic  acid.11 

In  order  to  prepare  it,  potassium  chlorate  is  gradually  add^d 
to  benzoic  acid  suspended  in  hydrochloric  acid ;  the  reaction, 

1  Henry,  Ber.  Dcutsch.  Chem.  Ges.  vi.  492. 

2  Brandes,  Arch.  Pharm.  xxiii.  15. 

3  Ann.  Chem.  Pharm.  xli.  48  ;  xlii.  265. 

4  Handb.  Org.  Chem.  iii.  92. 

5  Phil.  Mag.  xxvii.  129  ;  Ann.  Chem.  Pharm.  Ixv.  55. 

6  Ibid,  cxxii.  142.  7  Ibid.  cii.  259. 
8  Ibid,  cxxxiii.  293.  »  Ibid.  Ixx.  257. 

10  Gerhardt,  Traitt  Chim.  Org.  iii.  214.  -,  ' 

11  Wroblewsky,  Ann.  Chem.  Pharm.  clxviii.  200. 


220  AROMATIC  COMPOUNDS. 

which  proceeds  quietly,  must  be  occasionally  aided  by  gentle 
warming.  When  26  parts  of  chlorate  have  been  added  to 
10  parts  of  the  acid  and  about  90  parts  of  hydrochloric  acid, 
the  mixture  is  heated  to  boiling,  and  the  acid  which  separates 
on  cooling  converted  into  the  barium  salt,  which  is  then  purified 
by  re-crystallization. 

According  to  Hiibner  and  Weiss,  it  can  readily  be  obtained 
and  in  a  very  pure  condition  by  heating  7  grms.  of  benzoic 
acid  to  150°  with  4  grms.  of  manganese  dioxide  which  has 
been  washed  with  hydrochloric  acid,  and  40  grms.  of  fuming 
hydrochloric  acid,  and  re-crystalling  the  product  two  or  three 
times.1 

Properties. — It  dissolves  at  0°  in  2840  parts  of  water  (Kolbe 
and  Lautemann),  more  readily  in  hot  water  and  alcohol,  and 
crystallizes  in  concentrically  grouped  needles,  which  melt  at  153° 
and  readily  sublime.  On  fusion  with  caustic  potash  it  yields 
only  metahydroxybenzoic  acid  2 ;  it  does  not  melt  under  water. 

Calcium  metachlorobenzoate,  (C7H4C102)2Ca  +  3H2O,  forms 
scaly  crystals,  which  dissolve  in  82*6  parts  of  water  at  12°. 

Metachlorobenzoyl  chloride,  C6H4C1.COC1,  is  a  strongly  refrac- 
tive liquid,  boiling  at  2250.3 

MetacUoroUppuric  acid,  C6H4C1.CO.NHCH2.CO2H,  is  formed 
together  with  dichlorohippuric  acid  by  the  action  of  potassium 
chlorate  and  hydrochloric  acid  on  hippuric  acid,4  and  is  found 
in  the  urine  after  metachlorobenzoic  acid  has  been  administered.5 
It  is  a  tough,  amorphous  mass,  which  is  scarcely  soluble  in  cold, 
more  readily  in  boiling  water;  it  forms  crystalline  salts.  It 
decomposes  into  amido-acetic  acid  and  metachlorobenzoic  acid 
when  boiled  with  concentrated  hydrochloric  acid. 

Dichlorohippuric  acid,  C6H3C12.CO.NH.CH2.CO2H,  is  less 
soluble  in  hot  water  than  the  preceding  compound,  and  is  con- 
verted by  long  contact  with  water  into  a  granular  crystalline 
mass;  on  boiling  with  hydrochloric  acid  it  decomposes  into 
a-dichlorobenzoic  acid  and  amido-acetic  acid. 

Metachlorolenzonitril,  C6H4C1.CN,  was  prepared  by  Lim- 
pricht  and  Uslar  by  the  distillation  of  metasulphobenzamide, 
C6H4(CO.NH2)SO2.]NH2,  and  metasulphamidobenzoic  acid, 
C6H4(CO2H)SO2.NH2,  with  phosphorus  chloride.  It  crystallizes 

3  Her.  Deutsch.  CJwm.  Gcs.  vi.  175. 

3  Dembey,  Ann.  Chem.  Pharm.  cxlviii.  221. 

1  Limpricht  and  Uslar,  ibid.  cii.  262  ;  Graebe  ;  ibid,  cxxxviii.  197. 

4  Otto,  ibid,  cxxii.  129. 
8  Ibid,  cxlii.  346. 


PARACHLOROBENZOIC  ACID.  221 

from  alcohol  in  prisms,  which  smell  like  benzaldehyde,  melt 
at  40°,  and  readily  volatilize  with  steam.1 

Parachlorobenzoic  acid,  or  CJilorodracylic  acid,  was  first  obtained 
by  Beilstein  and  Wilbrand  from  paramidobenzoic  acid  by  the 
diazo-reaction.2  Beilstein  and  Geitner  then  prepared  it  by  the 
oxidation  of  parachloro toluene  with  chromic  acid  solution,3  while 
Emmerling  found  that  it  is  better  to  employ  crude  chlorotoluene 
and  a  dilute  solution  of  potassium  permanganate  for  this  pur- 
pose, the  orthochlorobenzoic  acid  formed  being  easily  removed 
by  boiling  water.4  Mliller  found  that  it  is  also  formed  when 
chlorobenzene  is  oxidized  with  manganese  dioxide  and  sulphuric 
acid,5  a  formation  corresponding  to  that  of  benzoic  acid  from 
benzene. 

Parachlorobenzoic  acid  dissolves  in  5288  parts  of  water  at  10°, 
crystallizes  from  alcohol  in  long,  lustrous  needles,  melts  at  236° 
and  sublimes  in  plates  at  a  higher  temperature. 

Calcium  parachlordbenzoate,  (C7H4ClO2).2Ca  +  3H2O,  crystal- 
lizes in  small  plates  or  needles,  and  is  even  less  soluble  in  water 
than  the  corresponding  salt  of  the  meta-acid. 

Paraclilorobcnzoyl  chloride,  C6H4C1.COC1,  is  a  heavy  liquid, 
which  fumes  in  the  air,  is  strongly  refractive,  and  boils  at 
220°— 222°  (Emmerling). 


DICHLOROBENZOIC  ACIDS,  C6H3C1.2.C02H. 

2125  a-Dichlorobenzoic  acid,  (3 : 4).  Otto  first  prepared  this 
compound  by  boiling  dichlorohippuric  acid  with  hydrochloric 
acid ; 6  it  is  also  obtained  by  the  oxidation  of  dichlorotoluene 
and  dichlorobenzyl  chloride,7  as  well  as  when  parachlorobenzoic 
acid  is  heated  to  200°  with  antimony  pentachloride.8 

It  is  formed,  together  with  the  following  compound,  by 
heating  benzoic  acid  with  bleaching  powder  solution,9  or  by  the 
action  of  potassium  chlorate  and  hydrochloric  acid,10  metachloro- 
benzoic  acid  being,  of  course,  the  first  product. 

It  is  slightly  soluble  in  cold,  more  readily  in  hot  water,  and 
crystallizes  in  fine,  lustrous  needles,  melting  at  201° — 202°. 

1  Ann.  Cham.  Pharm.  cvi.  32.  2  Ibid,  cxxviii.  270. 

3  Ibid,  cxxxix.  336.  4  Ber.  Deutsch.  Chem.  Ges.  viii.  880. 

6  Zeitschr.  Chem.  1869,  137.  6  Ann.  Chcm.  Pharm.  cxxii.  147. 

7  Beilstein  and  Kuhlberg,  ibid.  clii.  225  ;  Lellmann  and  Klotz,  ib id.  ccxxxi.  308. 

8  Beilstein,  ibid,  clxxix.  284. 

9  Claus  and  Thiel,  Bcr.  Deutsch.  Chem.  Gcs.  viii.  948. 
10  Claus  and  Pfeifer,  ibid.  v.  658  ;  vi.  721. 


222  AROMATIC  COMPOUNDS. 

fi-Dicklorobenzoic  acid,  (3:6),  is  formed  by  heating  ortho- 
chlorobenzoic  acid  with  hydrochloric  acid  and  potassium  chlorate 
or  potassium  dichromate,1  and  by  replacing  the  amido-group  of 
a-chloramidobenzoic  acid  by  chlorine.2  It  crystallizes  in  needles, 
which  melt  at  153'5°(Lellmann  and  Klotz)  and  dissolve  in  about 
1200  parts  of  cold  water. 

<y-Dichlorobenzoic  acid,  (2:6),  is  obtained,  together  with  the 
preceding  compounds,  when  dichlorobenzyl  chloride  is  heated 
with  water  to  200° ;  it  crystallizes  from  alcohol  in  small  needles, 
melting  at  126'5°.3 

S-Dichlorobenzoic  acid,  (2  :  4),  is  formed  by  the  oxidation  of  the 
corresponding  dichlorotoluene  with  nitric  acid,  and  crystallizes 
in  long,  pliable  needles,  melting  at  158°. 

e-Dichlorobcnzoic  acid,  (3  : 5),  has  also  been  prepared  from 
symmetric  dichlorotoluene,  and  forms  long  needles,  melting  at 
182°  (Lellmann  and  Klotz). 


TKICHLOROBENZOIC  ACIDS,  C6H2C13.CO2H. 

2126  a-Trichlorobenzoic  acid,  (2:4:6),  is  obtained  by  the 
oxidation  of  a-trichlorotoluene,4  and  by  heating  a-trichloro- 
benzyl  chloride 5  to  260°  with  water ;  it  crystallizes  in  needles 
which  melt  at  163°, 

ft-Trichlorobcnzoic  acid  has  been  obtained  from  the  corre- 
sponding aldehyde  by  oxidation  with  potassium  permanganate ; 
it  melts  at  1290.6 

y-Trichlorobenzoic  acid,  (3:4:  5),  is  formed  when  chrysanisic 
acid,  C6H2(NO2)2(NH2)CO2H,  is  heated  with  fuming  nitric  acid. 
It  forms  fine  needles,  melting  at  2030.7 


TETRACHLOROBENZOIC  ACID,  C6HC14.C02H. 

Beilstein  and  Kuhlberg  prepared  this  compound  by  heating 
tetrachlorobenzyl  chloride  with  water  to  280° 

1  Beilstein,  Ann.  Chem.  Pharm.  clxxix.  285. 

2  Rack  and  Wilkens,  ibid,  ccxxii.  201. 
*  Schultz,  ibid,  clxxxvii.  269. 

4  Jannasch,  ibid,  cxlii.  301 

6  Beilstein  and  Kuhlberg,  Ber.  Deutsch.  Chem.  Gcs.  xviii.  420. 

6  Seelig,  ibid,  xviii.  420. 

7  Salkowski,  Ann.  Chem.  Pharm.  clxiii.  28. 


THE  MONOBROMOBENZOIC  ACIDS. 


MONOBROMOBENZOIC  ACIDS,  C6H4Br.CO2H. 

2127  Orihobromobenzoic  acid  was  first  prepared  by  Griess 
from  anthranilic  acid  or  ortho-amidobenzoic  acid  by  the  diazo- 
reaction,  but  was  not  further  investigated  by  him.1  It  was,  how- 
ever, examined  by  v.  Bichter,  who  found  it  to  be  identical 
with  that  which  he  had  obtained  from  metabromonitrobenzene 
by  means  of  the  reaction  already  mentioned  (p.  21 7).2  Zincke 
obtained  it  by  boiling  orthobromotoluene  with  dilute  nitric 
acid ; 3  it  is,  however,  better  to  employ  a  dilute  solution  of 
potassium  permanganate.4 

It  is  more  readily  soluble  in  cold  water  than  its  isomerides, 
and  is  still  more  soluble  in  hot  water,  from  which  it  crystallizes 
in  long  needles,  which  melt  at  150°  and  sublime  in  small  plates. 

Barium  orthobromobenzoate,  (C7H4Br02)2Ba,  is  very  readily 
soluble  in  water,  and  crystallizes  from  alcohol  in  long  needles 
containing  two  molecules  of  alcohol. 

Mctabromobenzoic  acid.  Peligot  obtained  this  substance  in  the 
year  1838  by  the  action  of  bromine  on  silver  benzoate,5  and 
Herzog,  in  1842,  by  acting  upon  benzoic  acid  with  bromine  in 
the  sunlight.6  The  compound  thus  prepared,  however,  was  not 
pure.  Reinecke  then  found  that  the  pure  compound  can  readily 
be  obtained  by  heating  benzoic  acid  to  100°  with  bromine  and 
water ; 7  it  may  also  be  prepared  in  this  manner  from  benzamide, 
the  reaction  taking  place  at  120°, 8  and  bromanil  being  formed 
at  the  same  time : 

C6H5.CO.NH2  +  Br2  +  H2O  =  C6H4Br.C02H  +  N  H4Br. 

; 

According  to  Hiibner  and  Angerstein,  it  can  also  be  prepared 
by  Peligot's  method,  if  dry  silver  benzoate  be  submitted  to  the 
action  of  bromine  vapour  in  the  sunlight.9  Griess  also  obtained 
it  from  metamidobenzoic  acid 10  and  Sandmeyer  from  meta- 
bromaniline,  which  he  diazotized  and  brought  into  a  solution  of 
potassium  cuprous  bromide  heated  to  90° ;  the  nitril,  which  was 

1  Ann.  Chcm.  Pharm.  cxxxv.  121. 

2  Bcr.  Dcutsch.  Chcm.  Gcs.  iv.  464  ;  v.  428;  3  Ibid,  vii.  1502. 

1  Rhalis,  Ann.  Chcm.  Pharm.  cxcviii.  102.  6  Ibid,  xxviii.  246. 

6  Brandes,  Arch.  Pharm.  xxiii.  16. 

Zeitschr.  Chcm.  1865,  116;  1869,  100. 
*  Friedberg,  Ann.  Chcm.  Pharm.  clviii.  26. 
6  Ibid,  clviii.  2.  10  Ibid,  cxvii.  25. 


224  AROMATIC  COMPOUNDS. 

thus  formed,  was  then  decomposed  by  boiling  soda- solution;1 
Wroblewsky  prepared  it  by  the  oxidation  of  metabromotoluene.2 

Metabromobenzoic  acid  is  very  slightly  soluble  in  water, 
readily  in  alcohol,  crystallizes  in  needles,  melts  at  155°,  sublimes 
at  a  higher  temperature  and  boils  above  280°.  On  fusion  with 
caustic  potash,  metahydroxybenzoic  acid  is  formed  together  with 
a  little  salicylic  acid,  and,  probably,  some  parahydroxybenzoic 
acid. 

Barium  mctabromdbenzoate,  (C7H4BrO2)2Ba  +  4H2O,  is  very 
slightly  soluble  in  water  and  crystallizes  in  small,  flat  needles. 

Parabromobenzoic  acid  was  first  obtained  by  Griess  from  par- 
amidobenzoic  acid.3  It  is  formed  by  the  oxidation  of  parabromo- 
toluene,4  parabromo-ethylbenzene,5  etc.,  with  dilute  nitric  acid 
or  chromic  acid,  and  may  also  be  obtained  from  parabromaniline 
by  means  of  Weith's  reaction  (Part  III.  p.  31).6  It  is  almost 
insoluble  in  cold  water,  and  only  slightly  soluble  in  boiling  water, 
from  which  it  crystallizes  in  small  plates.  It  is  readily  soluble 
in  alcohol  and  ether,  and  separates  from  them  in  small  needles, 
melting  at  251°. 

Barium  parabromobenzoate,  (C7H4Br02)2Ba,  crystallizes  in 
nacreous  plates,  which  are  readily  soluble  in  water. 


DIBROMOBENZOIC  ACIDS,  C6H3Br2CO2H. 

Br.  :  Br.  Melting-point. 

a)  3  :  4  small  needles,7 229°— 230° 

/5)  2  :  3  small  needles,8 147° 

7)  3  :  5  flat  needles,9 213°— 214° 

8)  2  :  5  flat  needles,10 153° 

e)  2  :  4  needles  or  tablets,11     .     .     .  168°— 170° 


Bcr.  Dcntsch.  Chem.  Ges.  xviii.  1495. 
Ann.  Chem.  Pharm.  clxviii.  156. 
Ibid,  cxxxv.  121. 

Hiibner,  Ohly  and  Philipp,  ibid,  cxliii.  247. 
Fittig  and  Kbnig,  ibid,  cxliv.  283. 
Weith  and  Landolt,  Bcr.  Ueutsch.  Chem.  Ges.  viii.  717. 
Burghardt  and  Beutnagel,  Ann.  Chem.  Pharm.  ccxxii.  184. 
Beutnagcl,  ibid,  ccxxii.  105. 

Beilstein  and  Geitner,  ibid,  cxxxix.  4  ;  Neville  and  Whither,  Bcr.  Deutsch. 
Chem.  Ges.  xiii.  970. 

10  Holzapfel,  Ann.  Chem.  Pharm.  ccxxii.  107. 

11  Neville  and  Winther,  loc.  cit. 


IODOBENZOIC  ACIDS.  225 


TRIBROMOBENZOIC  ACIDS,  C6H2Br3.C02H. 

Melting-point, 
a)  silky  needles  l 234°— 235s 

/3)  small  needles 2 195° 

7)  needles3 186'5° 

8)  needles4  .     . 178° 


Pentabromobenzoic  acid,  C6Br5.CO2H.  When  metabromo- 
benzoic  acid  is  heated  to  150°  with  bromine  and  water, 
a-tribromobenzoic  acid  is  formed,  and  on  further  heating  with 
bromine  at  200°  is  converted  into  pentabromobenzoic  acid.  It 
crystallizes  from  alcohol  in  thin  plates  or  long,  broad  needles 
which  become  brown  and  melt  at  234° — 235°  (Reinecke). 


MONO-IODOBENZOIC  ACIDS,  C6H4I.CO2H. 

2128  Ortho-ioddbenzoic  acid  was  obtained  by  Griess  and  Bichter 
from  anthranilic  acid,  and  by  the  latter  also  from  meta-iodo- 
nitrobenzene.  Kekule  prepared  it  by  the  oxidation  of  ortho- 
iodotoluene  with  dilute  nitric  acid.  It  is  slightly  soluble  in 
water,  readily  in  alcohol,  and  crystallizes  in  long,  white  needles, 
which  melt  at  157°  and  readily  sublime.  On  fusion  with  potash, 
salicylic  acid  is  formed. 

Heta-iodobenzoic  acid  has  been  prepared  by  Griess,  Lunge,  and 
Hiibner,  and  by  Grothe  from  metamidobenzoic  acid.  It  is  also 
formed  when  benzoic  acid  is  heated  with  potassium  iodate  and 
dilute  sulphuric  acid,  and  by  the  action  of  iodine  and  iodic  acid 
on  sodium  benzoate.  It  forms  small  plates  or  needles,  melting 
at  186° — 187°;  on  heating  with  caustic  potash  solution  it  is  con- 
verted into  metahydroxybenzoic  acid,  and  with  ammonia  into 
metamidobenzoic  acid. 

Para-iodobenzoic  acid  was  obtained  by  Griess5  from  par- 
amidobenzoic  acid,  and  by  Korner6  by  the  oxidation  of  para- 
iodotoluene.  It  crystallizes  in  small  plates  melting  at  2560.7 

1  Reinecke,  Zeitechr.  Chem.  1869,  110. 

2  Smith,  £er.  Deuisch.  Chem.  Gcs.  x.  1706. 

3  Volbrecht,  ibid.  x.  1708. 

4  Lawrie,  ibid.  x.  1705. 

6  Ber.  Dcutsch.  Chem.  Gcs.  iv.  522. 

6  Zcitschr.  Chem.  1868,  327. 

7  Schmidt  and  Schultz,  Ann.  Chem.  Pharm.  ccvii.  333. 


226  ABOMATIC  COMPOUNDS. 

According  to  Beran  it  cannot  be  obtained  perfectly  pure  by 
recrystallization,  but  must  be  sublimed,  plates  which  melt  at 
265° — 266° l  being  obtained  in  this  way. 


MONOFLUORBENZOIC  ACIDS,  C6H4F.C02H. 

2129  These  compounds  are  obtained  by  passing  nitrogen 
trioxide  into  solutions  of  the  amidobenzoic  acids  in  alcohol, 
a  diazo-amidobenzoic  acid  being  formed,  which  is  decomposed 
into  fluorbenzoic  acid  and  amidobenzoic  acid  hydrofluoride  on 
warming  with  fuming  hydrofluoric  acid  : 2 

N.C6H4.C02H 

II  +  HF  =  C6H4F.C02H + NH2.C6H4.C02H+N2. 

N.NH.C6H4.C02H 

They  can  be  still  more  simply  obtained  from  the  diazobenzoic 
acid  sulphates  (p.  260). 

As  much  as  5  grms.  of  these  compounds  may  be  administered 
daily  to  a  dog  without  injuring  it;  they  appear  in  the  urine  as 
the  fluorhippuric  acids,3  C9H8FNO3,  which  crystallize  in  needles 
or  prisms. 

Orthofluorbcnzoic  acid  crystallizes  in  fine  needles,  is  readily 
soluble  in  alcohol,  more  readily  in  water,  and  melts  at  117° — 
118°. 

Orthofluorhippuric  acid  melts  at  121'5°. 

Metafluorbenzoic  acid  crystallizes  from  hot  water  in  broad, 
lustrous  plates  or  needles,  which  resemble  those  of  benzoic  acid 
and  melt  at  123°— 124°. 

Metafluorhippuric  acid  melts  at  152° — 153°. 

Parafluorbenzoic  acid  resembles  the  meta-compound,  and  melts 
at  180° — 181°.  This  substance  was  first  prepared  by  Schmitt 
and  v.  Gehren  from  ordinary  amidobenzoic  acid,  and  was  there- 
fore looked  upon  as  metafluorbenzoic  acid.  The  amido-acid 
employed  probably  contained  the  para-compound  as  an  im- 
purity. The  fluorbenzoic  acid  crystallizes,  according  to  their 
account,  in  pointed  rhombic  prisms,  which  have  a  characteristic 
sweet  taste,  and  melt  at  182°.  On  distillation  with  lime  it  yields 
phenol,  which  was  mistaken  by  Schmitt  and  v.  Gehren  for  fluor- 

1  Per.  Dculsch.Chcm   Ges.  xviii.  IS 7. 

3  Schmitt  and  v.  Gehren,  Journ.  Prdkt.  Chem.  [2]  i.  394  ;  Patern6  and  Oliveri, 
Gaz.  CTiim.  1882,  95.  8  Coppola,  ibid.  xiii.  521. 


THE  NITROBENZOIC  ACIDS.  227 

benzene ;  a  high  boiling  compound  is  also  formed,  which  probably 
consists  chiefly  of  diphenyl  oxide  : 1 

(C6H4F.C02)2Ca  +  2Ca(OH)2  =  2C6H5.OH  + CaF24  2CaC03. 

Parafluorhippuric  acid  melts  at  161'5°. 

Difluorbenzoic  acid,  C6H3F2.C02H,  is  formed,  together  with 
chromic  fluoride,  when  benzoic  acid  is  treated  with  chromium 
hexfluoride.  It  is  scarcely  soluble  in  cold,  only  slightly  in  boil- 
ing water,  but  more  readily  in  hot  benzene,  and  sublimes 
less  readily  than  benzoic  acid,  in  flat,  white  needles,  melting 
at  232°. 

Calcium  diftuorbenzoate,  (C6H3F2.CO2)2Ca  4-  3H2O,  crystallizes 
from  hot  water  in  fascicular  aggregates  of  white,  lustrous  needles, 
which  dissolve  in  200  parts  of  water  at  15°.2 


NITRO-SUBSTITUTION   PRODUCTS   OF 
BENZOIC  ACID. 

2130  In  the  year  1839,  Plantamour  obtained  an  acid  very  rich 
in  oxygen  by  the  action  of  nitric  acid  on  cinnamic  acid,  benzalde- 
hyde  being  also  formed.  He  gave  no  name  to  the  new  substance, 
since  he  wished  to  ascertain  by  investigation  whether  it  could  be 
classed  along  with  any  known  acid.  Analysis  led  to  the  formula 
C13H1009,  and  this  formula  was  confirmed  by  the  composition  of 
the  silver  salt.3 

In  the  next  year,  Mulder  found  that  nitrobenzinic  acid  is 
formed  by  the  action  of  nitric  acid  on  benzoic  acid,  cinnamic 
acid  and  oil  of  cinnamon.  He  determined  the  correct  com- 
position of  the  compound  and  formulated  it  as  C14H8O4  -f  N2O3 
+  H2O,  according  to  which  it  is  a  compound  of  nitrous  acid  with 
an  organic  substance  containing  two  atoms  of  hydrogen  less,  and 
one  atom  of  oxygen  more  than  benzoic  acid.  He  also  found  it 
to  be  identical  with  the  acid  discovered  by  Plantamour,  who  had 
overlooked  the  presence  of  nitrogen.4 

The  same  acid  was  prepared  by  Blyth  and  Hofmann  by  the 
distillation  of  styrolene  (phenylethylene)  with  strong  nitric  acid.5 

1  Patern6  and  Oliver!,  Gaz.  Chim,  xiii.  5?3. 

2  Jackson  and  Hartshorn,  Ber.  Deutsch.  Chem.  Gcs.  xviii.  1993. 

3  Ann.  Chem.  Pharm.  xxx.  348.  4  Ibid,  xxxiv.  297. 
5  Ibid.  liii.  304. 


2<J8  AROMATIC  COMPOUNDS. 

Abel  detected  it  among  the  products  of  the  action  of  nitric  acid 
on  cumene  (isopropylbenzene),1  and  Blumenau  obtained  it  in 
the  same  way  from  dragon's  blood.2  The  acid  formed  by  the 
nitration  of  benzoic  acid  was  then  investigated  by  Zinin,3 
Gerland,4  Voit5  and  Ernst,6  the  three  last-mentioned  giving 
directions  for  its  preparation. 

Glenard  and  Boudault  had,  in  1843,  obtained  nitrodracylic 
acid,  C8H6(NO2)O2,  by  the  action  of  fuming  nitric  acid  on  the 
dracyl  (toluene)  obtained  from  dragon's  blood,  and  Gerhardt 
considered  it  to  be  nitrobenzoic  acid.7  Wilbrand  and  Beilstein 
showed,  however,  that  it  is  not  identical,  but  isomeric  with 
the  latter,  and  that  another  acid  is  formed  in  small  quantity, 
which  appears  to  be  ordinary  nitrobenzoic  acid.8  It  was  ob- 
tained about  the  same  time  by  Fischer,  who  named  it  para- 
nitrobenzoic  acid,9  while  that  derived  from  benzoic  acid  was 
known  as  orthonitrobenzoic  acid  until  it  was  recognized  as 
oelonging  to  the  meta-series  (Part  III.,  p.  41). 

The  third  isomeride,  now  known  as  orthonitrobenzoic  acid, 
was  first  prepared  by  Radziswesky  from  phenylacetic  acid,  but 
was  believed  to  be  ordinary  nitrobenzoic  acid.10  Beilstein  and 
Kuhlberg  then  prepared  the  ortho-acid  from  cinnamic  acid 
(phenylacrylic  acid),11  and  considered  it  as  identical  with 
Radziswesky's  compound,  this  being  confirmed  by  Pirogow.12 

Griess  was  the  first  to  recognize  the  fact  that  not  only 
metanitrobenzoic  acid,  but  also  its  two  isomerides  are  formed  by 
the  nitration  of  benzoic  acid ;  from  4,000  grms.  of  benzoic  acid 
he  obtained,  in  addition  to  the  chief  product,  347  grms.  of 
orthonitrobenzoic  acid  and  35  grms.  of  paranitrobenzoic  acid,13 
while  according  to  Widnmann,  the  ortho-acid  formed  amounts  to 
25  per  cent,  of  the  weight  of  benzoic  acid  employed.14  The  older 
investigators  had  all  the  three  nitrobenzoic  acids  under  their  obser- 
vation, but  their  purest  compounds  were  probably  specimens  in 
which  one  or  other  of  the  isomerides  simply  predominated.  This 
is  shown  by  the  following  facts ;  toluene,  cumene,  styrolene,  oil 
of  cinnamon  and  cinnamic  acid  are  oxidized  by  dilute  nitric  acid 

1  Ann.  Chem.  Pharm.  Ixiii.  308.  2  Ibid.  Ixvii.  313. 

3  Journ.  Prakt.  Chem,.  xxxvi.  93. 

4  Ann.  Chem.  Pharm.  Ixxxvi.  143  ;  xci.  185. 

5  Ibid.  xcix.  100.  6  Zeituchr.  Chem.  1860,  477. 

1  Ann.  Chem.  Pharm.  xlviii.  343.  8  Ibid,  cxxvi.  255  ;  cxxviii.  257. 

9  Fischer,  ibid,  cxxvii.  137.  10  Ber.  Deutsch.  Chem.  Ges.  iii.  648. 

11  Ann.  Chum.  Pharm.  clxiii.  121.  12  Ibid,  clxiii.  140. 

13  Ibid,  clxvi.  129  ;  Ber.  Deutsch.  Chem.  Ges.  x.  1868. 

14  Ann.  Chem.  Pharm.  cxcliii.  223. 


ORTHONITROBENZOIC  ACID,  229 

to  benzole  acid,  which  is  converted  by  the  concentrated  acid  into 
the  nitrobenzoic  acids.  Toluene  is  converted  by  strong  nitric 
acid  into  the  three  isomeric  nitrotoluenes,  the  chief  product  being 
the  para-compound,  the  meta-compound  being  only  formed 
in  small  quantity  (p.  15),  while  on  the  nitration  of  benzoic 
acid,  the  meta-acid  forms  the  chief  product,  anol  the  para- 
compound  only  occurs  in  small  quantity.  Concentrated  nitric 
acid  converts  cinnamic  acid,  and  probably  styrolene  and  cumene, 
into  para-  and  ortho-nitro-compounds,  the  meta-compound 
being  possibly  formed  in  small  quantity.  All  these  nitro- 
derivatives  of  the  hydrocarbons,  as  well  as  the  nitro-cinnamic 
acids,  yield  the  corresponding  nitrobenzoic  acids  on  oxidation. 

Which  of  these  predominated,  therefore,  in  the  mixtures  in 
question,  depended,  in  the  first  instance,  upon  the  concentration 
of  the  nitric  acid  employed.  The  nitrobenzoic  acid  obtained 
from  cinnamic  acid  and  styrolene  was  probably  a  mixture  of  the 
para-  and  ortho-acids,  and  this  would  also  be  the  composition  of 
that  obtained  from  dragon's  blood  and  cumene  by  the  aid  of 
fuming  nitric  acid.  These  mixtures  may,  however,  have  also 
contained  dinitrobenzoic  acids  and  styphnic  acid,  both  of  which 
are  formed  by  the  action  of  nitric  acid  on  benzoic  acid. 


MONONITROBENZOIC  ACIDS,  C6H4(N02)C(XH. 

2131  OrtJionitrobenzoic  acid.  In  order  to  prepare  this  com- 
pound, the  mixture  obtained  by  the  nitration  of  benzoic  acid 
is  converted  into  the  barium  salts,  from  which  the  barium  ortho- 
nitrobenzoate  can  readily  be  obtained  in  crystals,  which  are  then 
decomposed  by  dilute  sulphuric  acid.1 

Orthonitrobenzoic  acid  can  also  be  readily  obtained  by  boiling 
orthonitrotoluene  for  a  long  time  with  a  solution  of  potassium 
permanganate.2  Crude  nitrotoluene  may  also  be  employed  since 
the  larger  portion  of  the  slightly  soluble  paranitrobenzoic  acid 
can  easily  be  separated.  The  barium  salts  are  prepared  from  the 
mother-liquors  of  this  and  separated  as  described  below.3 

Orthonitrobenzoic  acid  dissolves  in  100  parts  of  water  at  165°  ; 
it  is  more  readily  soluble  in  hot  water  and  crystallizes  from  it 
in  large  colourless  needles.  It  is  obtained  in  asymmetric  tablets 

1  Widnmann,  Ann.  Chem.  Pharm.  cxciii.  202. 

2  Widnmann,  Bcr.  Deutsch.  Chem.  Ges.  viii.  892. 
8  Moirnet,  Reverdin  and  Nolting,  ibid.  xii.  443. 

246 


230  AROMATIC  COMPOUNDS. 

or  prisms  by  the  spontaneous  evaporation  of  its  alcoholic  solution. 
It  melts  at  147°,  and  has  an  intensely  sweet  taste,  which  also 
characterizes  its  salts. 

Barium  orthonitrobenzoate,  (C6H4.NO2.C02)2Ba  +  3H2O,  crys- 
tallizes on  the  spontaneous  evaporation  of  its  solution  in  water, 
in  which  it  is  more  readily  soluble  than  the  acid,  in  large, 
yellow,  asymmetric  tablets,  which  lose  their  water  over  sulphuric 
acid. 

Ethyl  orthonitrobenzoate,  C6H4(NO2)CO2.C2H5,  forms  asym- 
metric crystals,  melting  at  30°. 

Orthonitrobenzoyl  chloride,  C6H4(N09)COC1,  is  a  faint  yellow 
liquid,  which  solidifies  at  a  low  temperature  to  a  crystalline  mass, 
and  decomposes  on  heating.  When  heated  with  silver  cyanide, 
the  nitril  of  nitrophenylglyoxylic  acid  is  formed,  and  this  is 
converted  by  reduction  into  isatin,  an  oxidation  product  of 
indigo.1 

Orthonitrobenzonitril,  C6H4(NO2)CN.  By  the  action  of  am- 
monia on  orthonitrobenzoyl  chloride,  orthonitrobenzamide, 
C6H4(N02)CO.NH2,  is  formed,  and  crystallizes  in  long  needles, 
melting  at  174° ;  it  is  converted  into  the  nitril  on  heating  with 
phosphorus  pentoxide.2  The  latter  may  also  be  obtained  syn- 
thetically from  orthonitraniline  by  diazotizing  it  with  hydro- 
chloric acid  and  sodium  nitrite,  and  bringing  the  compound 
thus  obtained  into  an  almost  boiling  solution  of  copper  sulphate 
and  potassium  cyanide  :  3 

2C6H4(N02)N2C1  +  Cu2(CN)2  =  2C6H4(N02)CN  +  N2+  Cu2Cl2. 

It  crystallizes  in  needles  which  are  readily  soluble  in  alcohol 
and  hot  water,  melt  at  109°,  and  sublime  when  more  strongly 
heated. 

2132  Metanitrobenzoic  acid  is  best  obtained  by  bringing  an  in- 
timate mixture  of  one  part  of  previously  fused  and  finely  powdered 
benzoic  acid  with  two  parts  of  nitre  into  three  or  four  parts  oi 
sulphuric  acid,  the  mixture  being  well  stirred,  and  then  heating 
until  the  nitrobenzoic  acids  have  separated  out  as  an  oily  layer.4 
In  a  well-conducted  operation  these  contain  little  or  no  unaltered 
benzoic  acid.  Should  this  be  present  in  large  quantity,  it  is 

1  Claissen  and  Shadwell,  Ber.  Dcutech.  Chem.  Ges.  xii.  350. 

2  Barthlein,  ibid.  x.  1713. 

3  Sandmeyer,  ibid,  xviii.  1492. 

4  Ernst,  loc.  cit.  ;  Leo  Liebermann,  Ber.    Deutsch.    Chem.   Ges.  x.  862  ;  Widn- 
mann,  Ann.  Chem.  Pharm.  cxciii.  216. 


METANITROBENZOIC  ACID.  231 

removed  by  distillation  with  water,  and  the  product  then  heated 
to  boiling  with  20  parts  of  water  and  neutralized  with  barium 
hydroxide.  Barium  metanitrobenzoate  crystallizes  out  on  cool- 
ing. The  mother  liquor  is  evaporated  and  the  residue  repeatedly 
extracted  with  small  quantities  of  cold  water,  the  salt  of  the 
ortho-acid  being  obtained  on  the  evaporation  of  the  solution.  A 
further  crop  of  crystals  of  the  meta-compound  are  obtained  by 
dissolving  the  residue  in  20  parts  of  boiling  water  and  cooling 
the  solution,  the  barium  salts  of  paranitrobenzoic  acid,  benzoic 
acid  and  styphnic  acid  remaining  in  solution. 

Metanitrobenzoic  acid  dissolves  at  16'5°  in  425,  and  at  100° 
in  10  parts  of  water ;  on  cooling  it  separates  from  the  solution  in 
small  plates ;  it  crystallizes  from  dilute  alcohol  in  monoclinic 
tablets,  melting  at  140° — 141° ;  when  gradually  cooled  the 
melting-point  falls  to  135° — 136°,  but  rises  again  after  some 
time,  or  when  the  remelted  acid  is  allowed  to  cool  rapidly 
(Widnmann).  It  possesses  the  characteristic  property  of  melting 
under  hot  water ;  it  commences  to  sublime  at  temperatures  above 
100°,  and  its  vapour  provokes  coughing. 

Sodium  metanitrobenzoate,  C6H4(NO2)C02Na  -f-  3H2O,  crystal- 
lizes in  coarse,  colourless  or  yellowish  tablets,  and  may  be 
employed  for  the  purification  of  the  crude  acid.1 

Barium  metanitrobenzoate,  (C6H4.NO2.CO2)2Ba  +  4H2O,  crys- 
tallizes in  thin  prisms,  and  is  less  soluble  than  the  free  acid. 

Ethyl  metanitrobenzoate,  C6H4(NO2)C02.C2H5,  has  been  pre- 
pared by  the  action  of  hydrochloric  acid  on  an  alcoholic  solution 
of  the  acid,  by  that  of  alcohol  on  its  chloride,  and  by  the  nitra- 
tion of  ethyl  benzoate.  It  is  also  formed  when  ethyl  nitrate 
and  benzoic  acid  in  ethereal  solution  are  treated  with  sulphuric 
acid.2  It  crystallizes  in  monoclinic  prisms,  which  melt  at  41° 
and  have  an  aromatic  smell,  boils  at  298°,  and  decomposes  into 
ethylene  bromide  and  metanitrobenzoic  acid  when  heated  to 
170°— 200°  with  bromine.3 

Metanitrobenzoyl  chloride,  C6H4(N02)COC1,  crystallizes  in 
pyramids  with  a  diamond  lustre  or  in  long,  fine  prisms,  which 
melt  at  33° — 34° 4  and  smell  like  benzoyl  chloride. 

Metanitrolenzamide,  C6H4(NO2)CO.NH2,  forms  yellow,  mono- 
clinic  needles,  and  melts  at  140°— 142°. 


1  Hiibner,  Ann.  Chcm.  Pharm.  ccxxii.  72. 

2  Fittica,  Journ.  Prakt.  Chem.  [2]  xvii,  221. 

3  Naumann,  Ann.  Chcm.  Pharm.  cxxxiii.  202. 

4  Claissen  and  Thompson,  Ber.  Dcutsch.  Chem.  Ges.  xii,  1943. 


AROMATIC  COMPOUNDS. 


Metanitrohippuric  acid,  C6H4(N02)CO.NH.CH2.CO2H.  Ber- 
tagnini  obtained  this  compound  in  the  year  1851  by  taking  6  grms. 
of  nitrobenzoic  acid  daily  and  isolating  the  nitrohippuric  acid  from 
his  very  acid  urine.  He  also  prepared  it  by  adding  sulphuric 
acid  to  a  solution  of  hippuric  acid  in  cold,  fuming  nitric  acid.  It 
crystallizes  from  alcohol  in  silky  needles,  melting  at  162°.  It  is 
decomposed  by  boiling  fuming  hydrochloric  acid  into  glycocoll 
and  nitrobenzoic  acid.1 

Metanitrobenzonitril,  C6H4(NO2)CN,  is  formed  by  the  action 
of  phosphorus  pentoxide  or  phosphorus  chloride  on  the  amide, 
as  well  as  by  the  nitration  of  benzonitril  and,  synthetically,  from 
metanitraniline  in  a  similar  manner  to  the  ortho-compound.  It 
crystallizes  in  needles,  melting  at  117° — 1180.2 

2133  Paranilrobenzoic  acid  is  prepared  by  the  oxidation  of 
paranitrotoluene  with  strong  nitric  acid  (Beilstein  and  Wilbrand ; 
Fischer),  with  potassium  dichromate  and  dilute  sulphuric  acid  3 
or  with  potassium  permanganate.4 

It  dissolves  in  1200  parts  of  water  at  17°,  and  in  140  parts  at 
100°  without  melting,  is  more  readily  soluble  in  alcohol  and 
crystallizes  in  yellowish  white,  lustrous  plates,  which  melt  at 
238°  and  sublime  in  needles. 

Barium  paranitrdbenzoate,  (C6H4.N02.C02)2Ba  +  5H2O,  crys- 
tallizes in  yellow,  transparent,  monoclinic  prisms,  which  dissolve 
in  250  parts  of  cold  and  8  parts  of  boiling  water.  It  forms  an 
anhydrous  double  salt  with  barium  benzoate,  (C6Hf).CO2).2Ba 
-f  (C6H4.NO2.C02)2Ba,  which  crystallizes  in  large,  colourless  or 
brownish,  lenticular  aggregates.  The  calcium  salt  and  calcium 
metanitrobenzoate  both  form  double  salts  with  calcium  benzoate.5 

Ethyl  paranitrol>enzoate)C6H.4(7$0^)C02.C2H.5,  forms  assymetric 
plates,  which  melt  at  57°,  and  are  converted  by  heating  with 
ammonia  into  paranitrobenzamide,  C6H4(N02)CO.NH2,  which 
crystallizes  in  needles  melting  at  197° — 198°. 

Paranitrobenzoyl  chloride,  C6H4(NO2)COC1,  boils  at  202°— 
205°  under  a  pressure  of  105  mm.,  and  crystallizes  from  petro- 
leum spirit  in  fine  needles,  melting  at  75°.6 

1  Ann.  Chem.  Pharm.  Ixxviii.  100  ;  Schwanert,  ibid.  cxii.  69  ;  Conrad.  Journ. 
Prakt.  Chem.  [2]  xv.  254. 

2  Beilstein,  Ann.  Chem.  Pharm.  cxlvi.  336  ;  Engler,  ibid,  cxlix.  297  ;  Schoppf, 
Ber.  Deutseh.  Chem.  Ges.  xviii.  1063. 

3  Beilstein  and  Geitner,  Ann.  Chem.  Pharm.  cxxxix.  335  ;  Kbrner,  Zeitschr. 
Chem.  1869,  635  ;  Rosenstiehl,  ibid.  1869,  701. 

4  Michael  and  Norton,  Bcr.  Deutseh.  Chem.  Ges.  x.  580. 

5  Salkowsky,  ibid.  ix.  24  ;  x.  1257. 

6  Gevekoht,  Ann.  Chem.  Pharm.  ccxxi.  335. 


PARANITROHIPPURIC  ACID.  233 

Paranitrobenzonitril,  C6H4(NO2)CN,  is  obtained  by  heating 
the  amide  with  phosphorus  pentoxide,1  as  well  as  by  diazotizing 
paranitraniline  and  pouring  the  solution  into  a  well  agitated 
solution  of  potassium  cuprous  cyanide  in  potassium  cyanide, 
heated  to  90°.2  It  crystallizes  from  alcohol  in  plates,  and 
sublimes  on  heating  in  long,  feathery  crystals,  melting  at  147°. 

ParanitroUppuric  acid,  C6H4(NO2)CO.NH.CH2.C02H,  is 
formed,  together  with  paranitrobenzoic  acid,  by  the  passage  of 
paranitro toluene  through  the  system  in  the  dog,  and  is  found  in 
the  urine  combined  with  urea.  It  crystallizes  from  hot  water  in 
orange-red  prisms,  melting  at  1290.3 

So-called  isomerides  of  the  three  nitrobenzoic  acids.  It  was 
early  stated  by  Mills  that  four  mononitrobenzoic  acids  exist,  and 
Fittica  thought  that  he  had  prepared  five  new  isomerides, 
differing  from  the  three  already  mentioned  in  their  melting 
points,  three  of  them  being  also  distinguished  by  their  citron- 
yellow  colour.  He  obtained  these  substances  "  by  peculiar 
methods,  which  chiefly  consisted  in  avoiding  with  the  greatest 
care  all  trustworthy  modes  of  purification,"  4  but  the  researches 
of  others  have  shown  that  his  compounds  do  not  exist.5  The 
melting  points  and  physical  properties  of  the  nitrobenzoic  acids, 
like  those  of  benzoic  acid  itself,  are  greatly  altered  by  very 
small  quantities  of  admixed  impurities ;  when  benzoic  acid  is 
nitrated,  small  amounts  of  the  dinitrobenzoic  acids  are  always 
formed  in  addition  to  the  three  mononitrobenzoic  acids,  and 
the  product  also  contains  benzoic  acid  and  styphnic  acid  (trini- 
troresorcinol),  the  latter  of  which  gives  it  its  yellow  colour. 

Bodewig  found  that  three  of  Fittica's  new  acids  are  simply 
impure  forms  of  metanitrobenzoic  acid,  which  he  obtained  from 
them  by  crystallization ;  the  two  others  gave  no  measurable 
crystals  ;  he  also  observed  that  this  acid,  besides  its  stable  form, 
exists  in  two  unstable  modifications,  which  also  crystallize  in  the 
monoclinic  system,  but  differ  from  the  stable  form  in  their 
crystallographic  constants.  Their  crystals  soon  become  opaque, 
from  the  formation  of  the  stable  form,  a  change  which  takes 
place  in  one  of  the  unstable  modifications  even  when  its  crystals 
are  allowed  to  remain  in  the  mother  liquor.  He  further 

1  Fricke,  Ber.  Deutsch.  Chem.  Ges.  vii.  1322. 
•  Sandmeyer,  ibid,  xviii.  1492. 

3  Jaffe.  ibid.  vii.  1673. 

4  Kekule,  Lehrb.  Org.  Ckem.  iii.  554. 

5  Erlenmeyer  and  Widnmann,  Ber.   Deutsch.   Chem.    Ges.   viii.    392  ;  Griess, 
ibid.  viii.  526  ;  Ladenburg,  ibid.  viii.   535  and  853  ;  Salkowsky,  ibid.   viii.  636  ; 
Liebermaun,  ibid.  x.  1036  ;  Glaus,  ibid.  xiii.  891  ;  Fittica,  ibid.  xiii.  1537. 


234  AROMATIC  COMPOUNDS. 

proved  their  identity  by  converting  them  into  the  ethyl  ether.1 
Fittica's  acids,  therefore,  have  no  more  real  existence  than 
salylic  acid  (p.  158). 


DINITROBENZOIC  ACIDS,  C6H3(NO2)3CO2H. 

2134  The  appended  numbers  indicate  the  position  of  the 
nitroxyls  when  that  of  the  carboxyls  is  1. 

a-Dinitrobenzoic  acid,  (2  :  5),  was  obtained  by  Griess,  together 
with  the  two  following  and  styphnic  acid,  by  heating  one  part 
of  orthonitrobenzoic  acid  with  ten  parts  of  a  mixture  of  equal 
amounts  of  fuming  sulphuric  and  nitric  acids.2  It  is  slightly 
soluble  in  cold  water,  and  on  evaporation  separates  out  in  prisms ; 
it  is  deposited  from  the  hot  saturated  solution  as  a  yellowish  oil, 
which  solidifies  in  needles,  melting  at  177°.  It  is  reduced  to 
a-diamidobenzoic  acid  by  tin  and  hydrochloric  acid. 

Barium  a-dinitrobenzoate,  (C6H3(NO2)2C02)<>Ba  +  4H2O,  forms 
long,  six-sided  plates,  which  are  slightly  soluble  in  cold,  more 
readily  in  hot  water. 

ft-Dinitrobenzoic  acid,  (2  :  4), 'is  also  formed  by  the  oxidation 
of  ordinary  dinitrotoluene  with  fuming  nitric  acid,3  and  by  the 
nitration  of  paranitrobenzoic  acid.4  It  melts  in  hot  water  and 
crystallizes  from  it  in  long,  lustrous,  brittle  needles,  or  on  spon- 
taneous evaporation  in  large,  rhombic  tablets  or  prisms,  which 
melt  at  179°  and  have  a  bitter  taste.  Tin  and  hydrochloric 
acid  convert  it  into  metadiamidobenzene,  carbon  dioxide  being 
eliminated. 

Barium  (3-dinitrobenzoate,  (C6H3(N02)2C02)2Ba  +  3H20,  is 
tolerably  soluble  in  cold  water  and  crystallizes"  in  white,  rhombic, 
or  six-sided  tablets. 

<y-Dinitrobenzoic  acid,  (2:6),  is  very  freely  soluble  in  boiling 
water,  crystallizes  in  fine,  matted,  white  needles,  melts  at  202°, 
and,  like  its  isomerides,  has  a  very  bitter  taste.  It  decomposes 
on  distillation  into  carbon  dioxide  and  metadinitrobenzene,  and 
on  reduction  yields  metadiamidobenzene. 

Barium  ry-dinitrobenzoate,  (C6H3(NO2)2CO2\Ba  +  2H2O,  is 
veiy  readily  soluble  in  water  and  crystallizes  in  needles. 

1  Bcr.  Deutsch.  Chem.  Ges.  xii.  1983  ;  Zeitschr.  Kryst.  iv.  58. 

2  Ber.  Deutsch.  Chem.  Ges.  vii.  1223. 

3  Tiemann  and  Judson,  ibid.  in.  223  ;  "Wurater,  ibid.  vii.  148. 

4  Glaus  and  Halberstadt,   ibid.  xiii.   815  ;    Stromeyer,  Ann.    Chem.   Pharm. 
ccxxii.  79. 


THE  DINITEOBENZOIC  ACIDS.  235 

S-Dinitrolcnzoic  acid,  (3  :  5),  or  Ordinary  dinitrobenzoic  acid., 
was  first  prepared  by  Cahours  : l  it  is  obtained  by  heating  ben- 
zoic  acid  2  or  metanitrobenzoic  acid  3  with  a  mixture  of  nitric 
and  sulphuric  acids,  or  by  oxidizing  symmetric  dinitrotoluene 
with  chromic  acid  4  or  nitric  acid  (Hiibner). 

In  order  to  prepare  it,  20  grms.  of  benzoic  acid  are  dissolved 
in  180  grms.  of  concentrated  sulphuric  acid,  one-third  of  the 
volume  of  fuming  nitric  acid  added,  and  the  whole  heated  nearly 
to  boiling  for  four  hours  and  then  poured  into  two  volumes  of 
cold  water  ;  a  yield  of  30  grms  is  obtained.5 

It  crystallizes  from  hot  water  in  thin,  quadratic  tablets,  and 
from  alcohol  in  prisms,  which  melt  at  204° — 205°,  and  sublime 
in  needles.  On  reduction  it  yields  S-diamidobenzoic  acid.  Its 
salts  detonate  violently  when  heated. 

Barium  §-dinitrobenzoate,  (C6H3(NO2)2CO2)2Ba  +  H20,  forms 
small  crystals,  readily  soluble  in  hot  water  (Hiibner). 

e-Dinitrobenzoic  acid,  (3:4),  is  formed  at  the  same  time  as  the 
/3-acid  by  the  action  of  a  mixture  of  nitric  and  sulphuric  acids 
on  paranitrobenzoic  acid.  It  has  an  intensely  bitter  taste,  is 
only  slightly  soluble  in  cold  water,  fuses  under  hot  water  and 
crystallizes  from  it  in  stellate  groups,  melting  at  161°.  These 
crystals  sublime  at  a  higher  temperature,  and  detonate  violently 
when  heated  on  platinum  foil.6 

Barium  e-dinitrobenzoatv,  (C6H3(N02)2C02)2Ba  +  4H90,  forms 
a  white,  radiating  crystalline  mass. 


TRINITROBENZOIC  ACID,  C6H2(N02)3C02H. 

2135  This  compound  is  obtained  by  heating  trinitrotoluene  to 
100°  with  fuming  nitric  acid  for  a  week.  It  crystallizes  from 
hot  water  in  rhombic  prisms,  melts  at  190°  and  sublimes  at  a 
higher  temperature.7 

1  Ann.  Chcm.  Pharm.  Ixix.  241. 

2  Michler,  ibid,  clxxv.  152. 

3  Muretow,  Zeitschr.  Chcm.  1870,  641. 

4  Stadel,  Ber.  Deutsch.  Chcm.  Ges.  xiv.  902. 
6  Hiibner,  Ann.  Chcm.  Pharm.  ccxxii.  72. 

6  Glaus  and  Halberstadt,  Ann.  Chcm.  Pharm.  xiii.  815. 

7  Tiemann  and  Judson,  ibid.  iii.  224. 


236  AEOMATIC  COMPOUNDS. 


CHLORONITROBENZOIC  ACIDS,  C6H3C1(N02)C02H. 

Cl :  N02  Melting-point. 

a)  2:5  silky  needles  or  rhombic  tablets l  .    .  164° — 165° 

£)  3:6  prisms2 137°— 138° 

7)  3:2  long,  thin  needles  or  six-sided  tablets 3          235° 

5)  3:5  small  needles 4       147° 

e)  4:3  small  needles 5       1 79°— 180° 

f)  2:4  readily  soluble  crystals  6 136°— 137° 

The  first  three  of  these  acids  have  been  obtained  by  the 
nitration  of  ortho-  and  meta-chlorobenzoic  acid.  The  fourth 
acid  is  prepared  from  the  corresponding  amidonitrobenzoic  acid 
and  the  fifth  by  the  nitration  of  parachlorobenzoic  acid ;  this 
compound  and  the  last  have  also  been  obtained  by  the  oxida- 
tion of  the  corresponding  chloronitrotoluenes.  Since  the  f-acid 
melts  at  the  same  temperature  as  the  yS-acid,  they  were 
considered  to  be  identical,  but  this  is  not  the  case,  as  the 
£-acid  is  derived  from  paranitrotoluene,  and  can  be  converted 
into  orthochlorobenzoic  acid. 


BROMONITROBENZOIC  ACIDS,  C6H3Br(NO2)CO2H. 

Br  :  NO2  Melting-point. 

a)     2:5     long  needles 7      177°— 178° 

/3)     3    6     monoclinic  prisms 8     .......  140°— 140° 

7)  3:2     monoclinic  crystals 9 250° 

8)  4:3     small  plates  or  needles10 199° 

e)     3:5     long  needles  or  thin,  six-sided  tablets n         161° 

0     2:4     long  needles 12 163°— 164° 


1  Kekule,  Ann.  Chem.  Pharm.  cxvii.  135;  Hiibner,  Zeitschr.  Chem.  1886,  614  ; 
Hiibner  and  Biedermann,  Ann.  Chem.  Pharm.  cxlvii.   263  ;  "Wilkens  and  Rack, 
ibid,  ccxxii.  192. 

2  Ulrich,  ibid,  ccxxii.  95.  3  Ibid. 

4  Grube,  Ber.  Deutsch.  Chem.  Ges.  x.  1703. 

5  Hiibner  and  Biedermann  ;  Raveill,  Ann.  Chem.  Pharm.  ccxxii.  182. 

6  Wachendorff,  ibid,  clxxxv.  275, 

7  Burghard,  Ber.  Deutsch.  Chem.  Ges.  viii.  560  ;  Rahlis,  Ann.    Chem.   Pharm. 
cxcviii.  109 ;  Scheufelen,  ibid,  ccxxxi.  181. 

8  Hiibner,  Ohly  and  Philipp,  ibid,  cxliii.   233  ;  Hiibner  and  Meeker,  Zeitschr. 
Chem.  1867,   565  ;  Hiibner  and  Petermann,   Ann.    Chem.  Pharm.  cxlix.   132  ; 
ccxxii.  101.  9  Ibid. 

10  Ibid.  ;  Raveill,  Ber.   Deutsch.    Chem.   Ges.  x.   1707  ;  Ann.   Chem.   Pharm. 
ecxxii.  177  ;  Scheufelen. 
11  Hesemann  and  Kb'hler,  ibid,  ccxxii.  166.  12  Scheufelen. 


ORTHO-AMIDOBENZOIC  ACID.  237 

The  first  is  formed  by  the  nitration  of  orthobromobenzoic 
acid,  as  well  as  by  the  oxidation  of  the  corresponding  bromo- 
nitrotoluene,  and  yields  8-dibromobenzoic  acid  when  the 
nitroxyl  is  replaced  by  bromine.  The  following  two  have  been 
prepared  from  rnetabromobenzoic  acid  and  are  converted  into 
anthranilic  acid  by  reduction  (Part  III.,  p.  50).  The  S-acid  is 
obtained  from  parabromobenzoic  acid  and  from  metanitrobromo- 
toluene,  the  e-acid  from  the  corresponding  amidonitrobenzoic 
acid,  and  the  f-acid  by  the  oxidation  of  the  corresponding 
bromonitrotoluene. 


IODONITROBENZOIC  ACIDS,  C6H3I(N02)C02H. 

I  :  NO2  Melting-point 

a)     3:2     slightly  soluble  crystals l 235° 

/3)     3  : 6     readily  soluble,  melts  under  water2    .    .    .       179° 

7)  3:4     readily  soluble,  does  not  melt  under  water3      192° 

8)  4:3     readily  soluble  in  alcohol,  very  slightly  in 

water* 210° 

The  first  three  are  formed  by  the  nitration  of  meta-iodobenzoic 
acid,  and  the  last  one  from  para-iodobenzoic  acid. 


MONAMIDOBENZOIC  ACIDS,  C6H4(NH2)C02H. 

2136  Ortho-amidobenzoic  acid.  Fritzsche,  in  his  research  on 
aniline,  mentioned  that  the  product  of  the  first  action  of  potash 
on  indigo  is  a  characteristic  acid,  which  he  subsequently  obtained 
pure  by  employing  indigo-blue  in  the  place  of  crude  indigo. 
He  determined  its  composition,  and  his  results  were  confirmed 
by  the  remarkable  decomposition  which  occurred  on  heating. 
"Anthranilic  acid  decomposes  when  it  is  heated  to  a  tempera- 
ture just  exceeding  its  melting-point  into  carbon  dioxide,  which 
is  given  off  as  a  gas,  and  aniline."  5 

Liebig  looked  upon  this  research  as  of  exceptional  interest, 
and  its  confirmation  appeared  to  him  to  be  so  important  and 

1  Cunze  and  Hiibner,  ibid,  cxxxv.  106  ;  Grothe,  Journ.  PraU.  Chem.  [2]  xviii. 
324.  2  Ibidf 

4  Glassner,  Her.  Deutsch.  Chem.  Ges.  viii.  562. 

5  Journ.  Prakt.  Chem.  xxiii.  67  ;  Ann.  Chem.  Pharm.  xxxix.  76. 


238  AROMATIC  COMPOUNDS. 

necessary,  that  lie  instituted  further  investigations,  which  cor- 
roborated the  results  obtained  by  Fritsche.1  At  the  same  time 
he  discovered  an  excellent  method  for  the  preparation  of 
anthranilic  acid,  which  will  be  described  below. 

Gerland  subsequently  showed  that  the  acid  in  question  is 
isomeric  with  benzamic  acid  (metamidobenzoic  acid).2  Hiibner 
and  Petermann  succeeded  in  preparing  anthranilic  acid  syn- 
thetically from  benzoic  acid ;  by  the  nitration  of  metabromo- 
benzoic  acid,  they  obtained  two  isomeric  nitrobromobenzoic 
acids,  C6H3Br(N02)C02H,  both  of  which  yielded  anthranilic 
acid  on  reduction  (Part  III.,  p.  50).  It  may  be  more  simply 
obtained  by  the  reduction  of  orthonitrobenzoic  acid  with  tin  and 
hydrochloric  acid;3  the  tin  is  precipitated  with  sulphuretted 
hydrogen  and  the  filtrate  evaporated  to  dryness,  the  residue 
treated  with  an  excess  of  ammonia  and  the  solution  then 
acidified  with  acetic  acid.  The  greater  portion  of  the  anthra- 
nilic acid  crystallizes  out ;  the  remainder  is  then  obtained  as  the 
copper  salt  by  the  method  described  below. 

Sandmeyer  observed  that  almost  half  of  the  nitrobenzoic 
acid  is  converted  into  salicylic,  acid  on  reduction  with  tin  and 
hydrochloric  acid.4 

In  order  to  prepare  it  from  indigo,  the  crude  material  is  finely 
powdered  and  boiled  for  ten  hours  with  ten  times  its  amount  of 
strong  caustic  potash  solution,  a  small  quantity  of  manganese 
dioxide  being  occasionally  added,  and  the  original  volume  of  the 
solution  maintained  throughout  the  operation  by  the  repeated 
addition  of  small  quantities  of  water.  The  solution  is  then 
neutralized  with  sulphuric  acid,  freed  from  most  of  the  potassium 
sulphate  by  crystallization  and  evaporated  to  dryness.  Potassium 
anthranilate  is  extracted  from  the  residue  by  alcohol  and  is  then 
converted  into  the  copper  salt,  which  is  obtained  as  a  light  green 
precipitate  by  distilling  off  the  alcohol,  acidifying  with  acetic 
acid  and  adding  copper  acetate  or  sulphate;  the  free  acid  is 
obtained  from  this  by  the  action  of  sulphuretted  hydrogen.5 
Bottinger  found  that  the  only  definite  compound  formed  in  this 
reaction,  in  addition  to  28  per  cent,  of  anthranilic  acid,  is  formic 

acid : 6 

C16H10N202 + 2O  +  4H2O  =  2C7H7N02  +  2CH202. 

Ann.  Chem.  Pharm.  xxxix.  91.          2  Ibid.  Ixxxvi.  143. 
Beilstein  and  Kuhlbcrg,  Ann.  Chcm.  Pharm.  clxiii.  138. 
Ber.  Dcutsch.  Chem.  Gcs.  xviii.  1494. 
Hiibner  and  Petermann,  Ann.  Chem.  Pharm.  cxlix.  142. 
Ber.  Dcutsch.  Chcm.  Gcs.  x.  269. 


PROPERTIES  OF  ORTHO-AMIDOBENZOIC  ACID.          239 

Ortho-amidobenzoic  acid  dissolves  in  about  250  parts  of  cold, 
more  readily  in  hot  water,  and  readily  in  alcohol.  The  solution 
has  a  sweet  taste,  but  is  acid  to  litmus  paper,  and  shows  a  blue 
fluorescence  when  the  acid  is  pure.  It  crystallizes  in  small 
plates,  or  on  the  gradual  evaporation  of  its  solution,  in  rhombic 
needles,  melts  at  145°,  and  sublimes  when  carefully  heated,  but 
decomposes  into  carbon  dioxide  and  aniline  when  distilled,  more 
completely  when  mixed  with  powdered  glass  (Liebig).  On 
treatment  with  sodium  amalgam,  benzoic  acid  and  ammonia  are 
formed  (Hiibner  and  Petermann)  : 

C6H4(NH2)C02H  +  2H=C6H5.C02H  +  NH3. 

Most  of  its  metallic  salts  crystallize  well. 

Ortho-amidobenzoic  acid  hydrockloride,  C7H7NO2.HC1,  is  readily 
soluble  in  water  and  alcohol,  slightly  in  ether,  and  crystallizes  in 
needles  or  four-sided  prisms,  melting  at  191°;  its  solution  is  not 
precipitated  by  platinum  chloride. 

Formortho-amidobenzoic  acid,  2C6H4(NH.CHO)C02H  +  H2O, 
is  obtained  by  heating  ortho-amidobenzoic  acid  with  formic  acid, 
and  crystallizes  from  chloroform  in  fine,  matted  needles,  which, 
after  drying,  form  a  light,  very  readily  electrified  mass,  and  melt 
at  168°.  When  it  is  heated  with  phosphorus  pentoxide,  phenyl 
carbamine  is  formed.1 

Acctortlio-amidobenzoic  acid,  C6H4(NH.C2H30)C02H,  is  formed 
by  the  oxidation  of  acetorthotoluide  with  potassium  perman- 
ganate,2 and  by  heating  a  mixture  of  equal  molecules  of 
anthranilic  acid  and  acetic  anhydride.3  It  is  slightly  soluble  in 
cold,  readily  in  hot  water,  and  crystallizes  from  acetic  acid  in 
flat,  rhombic  needles,  which  melt  at  179° — 180°. 

Diacetortho-amidobenzoic  acid,  C6H4N(C2H3O)2CO2H,  is  ob- 
tained by  boiling  anthranilic  acid  with  an  excess  of  acetic 
anhydride,  and  forms  crystals,  melting  at  220°  (Bedson  and 
King). 

Benzortho-amidobenzoic  acid,  C6H4(NH.CO.C6H5)CO2H,  is 
formed  by  the  action  of  benzoyl  chloride  on  anthranilic  acid 
id  by  the  oxidation  of  benzoylorthotoluide.  It  crystallizes 
:om  alcohol  in  long  needles,  melting  at  1820.4 

1  v.  Meyer  and  Bellmann,  Journ.  PraH.  Chem.  [2]  xxxiii.  24. 

2  Bedson  and  King,  Ber.  Deutsch.  Chem.  Ges.  xiv.  263. 

3  Jackson,  ibid.  xiv.  886. 

4  Bruckner,  Ann.   Chem.   Pharm.  ccv.  134. 


240  AROMATIC  COMPOUNDS. 

Ortho-amidobenzamide,  C6H4(NH2)CO.NH2,  is   formed  when 
anthranilcarboxylic  acid  is  dissolved  in  aqueous  ammonia  : 

CO  CO.NH2 


C6H4       |  +  NH3  =  C6H  +  C0 

N.C0H 


It  crystallizes  from  hot  water  in  nacreous  plates,  and  from 
chloroform  in  large,  white  plates,  melts  at  108°,  and  boils  with 
slight  decomposition  at  about  300°.  It  is  converted  into  ortho- 
amidobenzoic  acid  by  acids  and  alkalis.1 

Ortho-amidobenzonitril,  C6H4(NH2)CN,  is  obtained  by  the 
action  of  tin  and  hydrochloric  acid  on  orthonitrobenzonitril ;  it 
crystallizes  in  yellowish  needles,  melts  at  103°,  and  forms  readily 
soluble  salts.2 

2137  Anthranil,  C7H5NO,  is  formed  by  the  action  of  tin  on  a 
solution  of  orthonitrobenzaldehyde  in  glacial  acetic  acid,  and  is 
a  colourless,  oily  liquid,  which  has  a  characteristic,  penetrating 
smell,  is  volatile  with  steam,  and  commences  to  boil  at  210° — 215°, 
the  greater  portion  of  it  being  decomposed.  It  rapidly  becomes 
brown  and  resinous  when  exposed  to  the  air  or  to  light.  It  is  a 
very  feeble  base,  and  combines  with  mercuric  chloride  to  form  the 
compound  C7H5NO  +  HgCl2,  which  crystallizes  in  fine  needles 
and  is  readily  soluble  in  alcohol  and  hot  water,  but  on  heating 
with  a  solution  of  potassium  chloride,  is  resolved  into  its 
constituents.3 

Anthranil  is  converted  into  anthranilic  acid  by  the  action  of 
alkalis : 

/CO  /CO.OH 

C6H4<   | 
\NH 


When  heated  with  ammonia  and  ferrous  sulphate  it  is  con- 
verted into  orthonitrobenzaldehyde,  while  antkranilcarboxylic 
acid  is  formed  when  it  is  heated  with  ethyl  chlorocarbonate  : 

/CO  /CO 

C6H4<    |     +COC1(OC2H6)  =  C6H4<    |  +C2H5C1. 

\KCO.OH 


This  compound  crystallizes  from  hot  water  in  fine  needles, 
which  decompose  into  carbon  dioxide  and  anthranil  at  230°.     It 

1  Kolbe,  Journ.  PraU.  Chem.  [2]  xxx.  475. 

2  Barthlein,  Ber.  Dcutsch.  Chem.  Gei.  x.  1713. 

3  Friedlanderand  Henriques,  ibid.  xv.  2105. 


BENZOYLANTHRANIL.  241 

dissolves  in  dilute  caustic  soda,  forming  a  solution  which  possesses 
a  splendid  blue  fluorescence;  this,  however,  soon  disappears, 
anthranilic  acid  being  formed.  Anthranilcarboxylic  acid  is  also 
obtained  by  the  oxidation  of  isatin,  and  will  be  more  fully 
described  along  with  this  substance. 

Benzoylanthranil  is  readily  obtained  by  the  action  of  benzoyl 
chloride  on  anthranil : 

/CO  /CO 

C6H4<  |      +  COC1.C6H5  =  C6H4<   |  +  HC1. 

\NH  \N.CO.C6H5 

It  crystallizes  from  a  mixture  of  benzene  and  ligroin  in  long 
needles,  which  melt  at  122° — 123°,  and  dissolve  when  heated 
with  dilute  alkalis,  benzortho-amidobenzoic  acid  being  formed.1 

Dicyanamidobenzoyl,  C9H5N30,  is  the  name  given  by  Griess  to 
a  compound  which  he  obtained  by  passing  cyanogen  into  a  cold 
aqueous  solution  of  anthranilic  acid  : 


NH-C-CN 

^2=C6H4<  ||          +H20. 

XCO.OH  XX)  -  N 

It  is  slightly  soluble  in  water,  readily  in  hot  alcohol,  and 
crystallizes  in  small,  yellowish  prisms  ;  although  it  does  not 
contain  a  carboxyl  group,  it  has  an  acid  reaction  and  is  a 
monobasic  acid.2 

Carboxamidocyanamidobenzoyl,  C9H7N302,  is  formed  when  the 
preceding  compound  is  heated  with  strong  ammonia  in  a  sealed 
tube : 

/NH-C-CN  /NH-C-CO.NIL. 


C6H4  ||          +H20  =  C6H4  || 

XX) -N  XCO-N 

It  crystallizes  from  hot  water  in  fine  needles  and  from  alcohol  in 
plates,  has  an  acid  reaction  and  forms  salts  with  bases,  the  hydrogen 
of  the  imido-group  being  probably  replaced  by  the  metal. 

Carboxylcyanamiddbenzoyl,  2C9H6N2O3+H2O,  is   obtained   by 
heating  dicyanamidobenzoyl  with  baryta  water: 

NH-C-CN  /NH-C-CO.OH 

C6H4<  ||  +2H20  =  C6H/  ||  +NH3. 

\CO-N  XX) -N 

1  Friedlander  and  Wleiigel,  Ber.  Dcutsch.  Chem.  Ges.  xvi.  2227. 

2  Ibid.  xi.  1986  and  2180. 


242  AROMATIC  COMPOUNDS. 

It  crystallizes  in  small,  white  plates,  which  are  slightly  soluble 
in  cold  water  and  alcohol;  it  is  a  dibasic  acid.  When  it  is  boiled 
with  water  or  acids,  or  simply  heated,  carbon  dioxide  is  evolved 
and  carbimidamidobenzoyl,  C8H6N2O2,  formed.  This  compound 
crystallizes  from  hot  water  in  needles  melting  at  214°.  It 
possesses  basic  properties  and  has  the  following  constitution  : 


—  CH 

|| 
CO-N. 

Griess  has  also  prepared  various  other  derivatives  of  dicyan- 
amidobenzoyl.1 

Ethoxycyanamidobenzoyl,  C10H10N2O2,  is  formed  when  an 
alcoholic  solution  of  anthranilic  acid  is  saturated  with  cyanogen, 
allowed  to  stand  for  some  time  and  then  evaporated  : 


, 
C6H4< 

XCO.OH 

/NH—  C—  OC2H5 
C6H4<  || 

\CO-N 

It  crystallizes  from  hot  alcohol  in  needles,  melts  at  173°,  and 
can  be  distilled  in  small  quantities  without  undergoing 
decomposition.2 

2138  Uramidobenzoyl,  C8H6N2O2,  is  prepared  by  fusing 
anthranilic  acid  with  urea  or  by  boiling  the  preceding  com- 
pound with  hydrochloric  acid  : 

NH—  C—  OC2H5  ,NH—  CO 


It  is  slightly  soluble  in  water  and  alcohol,  crystallizes  in  lustrous 
plates  melting  above  350°,  dissolves  in  caustic  potash  solution 
and  is  reprecipitated  by  carbon  dioxide.  Fuming  nitric  acid 
converts  it  into  nitro-uramidobenzoyl,  C8H5(N02)N2O2,  which 
crystallizes  in  honey-yellow  prisms,  and  is  converted  by  reduction 
into  the  slightly  soluble  amido-uramidobenzoyl,  C8H5(NH2)N2O2, 

1  Bcr.  Deutsch.  Chem.  Ges.  xviii.  2417. 

2  Griess,  ibid.  ii.  415. 


BENZOYLGUANIDINE.  243 

which  forms  yellow  needles  and  yields  salts,  which  are  also  only 
slightly  soluble  and  crystallize  well  (Griess). 

Ortho-uramidobenzoic  acid,  C8H8N203.  This  compound,  which 
is  the  acid  corresponding  to  the  anhydride  just  described,  is 
formed  by  the  action  of  potassium  cyanate  on  ortho-amidobenzoic 
acid  hydrochloride : l 

/NH2  /NH.CO.NH2 

C6H4<  +CONH=C6H4< 

\C02H  \C02H. 

It  crystallizes  in  needles,  and  on  treatment  with  nitric  acid 
only  yields  one  dinitro-compound,  which  will  be  subsequently 
mentioned. 

Orthobenzoglycocyamidine,  or  Benzoylguanidine,  C8H7N3O,  is 
obtained  by  heating  ethoxycyanamidobenzoyl  with  alcoholic 
ammonia  : 

^NH-C— OC2H5 

l\CO  — N 

[— C=NH 


It   may  also   be   obtained   by   allowing   a   solution   containing 
cyanamide  and  anthranilic  acid  to  stand  :  2 


C6H4.NH2  C6H4  —  NH 

+  CN.NH2=  |  >C 

CO.OH  CO  -  NH 


It  crystallizes  in  nacreous  plates,  which  are  only  slightly  soluble 
in  water  and  alcohol. 

Benzoylguanidine  nitrate,  CgHgNgO.NOg,  is  a  very  characteristic 
salt  ;  it  crystallizes  in  small  plates,  which  are  almost  insoluble  in 
water  and  alcohol. 

2139  a-MethylortJiobenzoglycocyamidine,  or  a-OrtJidbenzocreatin- 
ine,  G8H6(CH3)N3O,  is  formed  when  a  strongly  alkaline  solution 
of  the  preceding  compound  is  treated  with  methyl  iodide  and 
allowed  to  stand  for  some  days.  It  is  almost  insoluble  in  cold, 
slightly  soluble  in  hot  water,  more  readily  in  boiling  alcohol,  and 

1  Griess,  Journ.  PraJct.  Chem.  [2]  v.  371. 

2  Griess,  Ber.  Deutsch.  Chem.  Ges.  xiii.  977. 


244  AROMATIC  COMPOUNDS. 

crystallizes  in  lustrous  needles,  which  have  a  slightly  bitter  taste 
and  a  neutral  reaction.  The  hydrochloride,  C9H9N3O.C1H, 
crystallizes  in  narrow  plates,  which  readily  dissolve  in  water 
without  decomposition. 

/3-Orthobenzocreatinine  is  obtained  by  heating  ethoxycyan- 
amidobenzoyl  with  aqueous  methylamine.  It  resembles  the 
a-compound  in  forming  lustrous  needles,  which  have  a  very 
faintly  bitter  taste,  but  differs  from  it  in  being  soluble  in  baryta 
water  and  caustic  potash  solution,  and  in  forming  salts  which 
are  decomposed  by  water. 

The  constitution  of  these  compounds  is  shown  by  the  following. 
formulae : 

C6H4  —  N.CH3  C6H4—  NH 

>C=NH  >C=NH. 

CO NH  CO NCH3 

Oxalanthranilic  acid,  or  Orthobenzamoxalic  acid,  C9H7NO6-j-H20. 
Friedlander  and  Ostermaier  first  obtained  this  compound  by  the 
oxidation  of  carbostyril,  C9H7lNi  O,  with  potassium  permanganate? 
and  named  it  carbostyrilic  acid.  They  then  found  that  on 
heating  with  dilute  hydrochloric  acid  or  caustic  soda  solution  it 
decomposes  into  anthranilic  acid  and  oxalio  acid.1  Kretschy 
recognized  it  by  this  property  as  identical  with  the  cynuric  acid 
which  is  formed  by  the  oxidation  of  cynurenic  acid,  C9H6NO 
(CO2H),  a  substance  occurring  in  the  urine  of  the  dog.  He 
also  prepared  it  by  gradually  heating  oxalic  acid  to  150°  with 
anthranilic  acid : 2 

,NH2  /NH.CO.OH 

C6H4<  +  HO.CO.CO.OH=C6H4<  +H2O. 

\CO.OH  \CO.OH 

It  has  also  been  obtained  by  the  oxidation  of  other  substances, 
which,  like  those  just  mentioned,  are  derivatives  of  quinoline,  a 
compound  which  has  the  following  constitution  : 

HC      N 

HC      C      CH 

II       I 
C      CH 


CH      CH 

1  Griess,  Ber.  Deutsch.  Chem.  Ges.  xv.  332.  2    Monatshcft  Chem.  v.  16. 


DINITRODIPHENYLAMINE-ORTHOCARBOXYLIC  ACID.     245 

Oxalanthramlic  acid  is  slightly  soluble  in  cold  water,  readily 
in  alcohol  and  ether,  and  crystallizes  from  the  latter  in  hard 
needles  united  to  form  druses.  It  is  a  powerful  dibasic  acid. 

Normal  calcium  benzamoxalale,  2C9H5NO5Ca-f  5H2O,  is  the 
most  characteristic  salt  of  this  acid.  It  separates  out  in 
glittering  prisms  when  calcium  chloride  is  added  to  a  solution  of 
the  ammonium  salt. 

2140  Dinitrudiplienylamine-ortJiocarboxylic  acid,  C6H4(NH. 
C6H3(NO2)2)C02H,  is  formed  when  anthranilic  acid  is  heated 
with  chlorodinitrobenzene,  (Cl  :  NO2  :  N02  =  1  :  2  :  4),  and  an 
excess  of  ammonia  : 


C6H4  +  C6H3C1(N02)2+  2NH3= 

\CO.OH 


C6H4  +NH4C1. 

\CO.ONH4 

The  ammonium  salt  produced  in  this  way  forms  lustrous,  ruby- 
red  plates  ;  the  free  acid  is  obtained  by  the  addition  of  strong 
hydrochloric  acid  to  this  salt,  and  is  almost  insoluble  in  water, 
only  very  slightly  soluble  in  cold  alcohol  and  glacial  acetic  acid, 
crystallizing  from  a  hot  mixture  of  these  in  small,  orange-yellow, 
matted  needles,  which  fuse  at  262°  —  264°  to  a  brownish  red 
liquid,  which  appears  almost  black  when  seen  in  thick  layers  ; 
when  it  is  carefully  heated  a  portion  distils  without  decomposi- 
tion, but  it  detonates  when  rapidly  heated  on  platinum  foil. 

Its  alkaline  salts  are  slightly  soluble  in  cold*  more  readily  in 
hot  water,  and  crystallize  in  reddish  yellow  to  ruby-red  plates, 
which  detonate  on  heating.  All  the  other  salts  are  almost 
insoluble.  The  barium  salt  is  a  dark  cinnabar-red  precipitate. 

This  compound  does  not  yield  the  corresponding  amido-acid 
on  reduction  with  tin  and  hydrochloric  acid,  but  this  is  converted 
into  diamidohydro-acridine  Jcetone  with  elimination  of  water  ;  this 
substance,  which  will  be  subsequently  described,  has  the  follow- 
ing constitution  : 

CH  NH  CNH 


HC      C      C      CH 

I       II      I!      I 
HC      C     C      CNH2 


CH  CO   CH 

247 


246  AROMATIC  COMPOUNDS. 

Other  amido-acids,  in  which  the  carboxyl  does  not  stand 
in  the  ortho-position  to  the  amido-group,  also  yield  dinitro- 
diphenylaminecarboxylic  acids  with  chlorodinitrobenzene,  but 
these  are  converted  by  reduction  into  the  corresponding  diamido- 
acids. 

This  reaction,  therefore,  may  be  employed  as  a  ready  method 
for  ascertaining  whether  or  not  an  aromatic  arnido-acid  belongs 
to  the  ortho-series.  The  compound  to  be  tested  is  heated  to 
boiling  with  chlorodinitrobenzene,  alcohol  and  some  ammonia 
for  some  time.  If  an  ortho-compound  be  present,  the  product 
yields  on  reduction  a  base  insoluble  in  alkalis ;  in  other  cases 
an  acid  is  obtained.1 

2141  Metamiddbenzoic  acid.  Zinin  obtained  this  compound  in 
1845  by  the  action  of  ammonium  sulphide  on  nitrobenzinic  acid 
(metanitrobenzoic  acid)  and  named  it  benzamic  acid.2  Chancel, 
in  1849,  converted  nitrobenzamide  into  amidobenzamide  by  the 
same  method,  but  he  looked  upon  the  substance  obtained  as 
aniline  urea  and  named  it  carbanilamide.  By  boiling  it  with 
caustic  potash  solution  he  obtained  carbanilidic  acid,  which 
Gerland  subsequently  proved  to-  be  identical  with  benzamic  acid.3 
Voit,  who  investigated  its  salts,  remarked  that  the  latter  name 
is  unsuitable,  since  only  the  radicals  of  dibasic  acids  form  amic- 
acids,  and  he  therefore  proposed  the  name  amidobenzoic  acid.4 

In  order  to  prepare  it,  a  solution  of  metanitrobenzoic  acid  in 
strong  ammonia  is  saturated  with  sulphuretted  hydrogen  in 
absence  of  air,  concentrated  and  treated  with  acetic  acid.  Meta- 
nitrobenzoic acid  may  also  be  reduced  with  tin  and  hydrochloric 
acid  and  the  double  tin  salt  of  the  amido-acid  decomposed  with 
sulphuretted  hydrogen.  The  amidobenzoic  acid  is  then  pre- 
cipitated from  the  nitrate,  previously  neutralized  with  ammonia, 
by  acetic  acid. 

It  is  slightly  soluble  in  cold,  more  readily  in  hot  water  and 
alcohol,  and  crystallizes  in  warty  masses  of  needles,  which  melt 
at  174°  and  partially  volatilize  at  a  higher  temperature  without 
decomposition  ;  when  it  is  heated  with  spongy  platinum  (Chancel) 
or  baryta,  it  decomposes  into  carbon  dioxide  and  aniline.  Its  solu- 
tion has  an  acid  reaction  but  a  sweet  taste,  and  decomposes  in 
the  air  with  separation  of  a  brown  powder,  its  alkaline  solution 

1  Jourdan,  Ber.  Deutsch.  Chem.  Ges.  xviii.  1444. 

2  Journ.  Prakt.  Chem.  xxxvi.  93. 

3  Ann.  Chem.  Pharm.  Ixxxvi.  142. 
*  Ibid.  xcix.  100. 


METAMIDOBENZOIC  ACID.  247 

behaving  in  a  similar  manner.  Its  metallic  salts  crystallize 
well. 

Metamidobenzoic  acid  hydrochloride,  C7H7NO2.C1H,  crystallizes 
in  prisms,  which  are  readily  soluble  in  water,  slightly  in  hydro- 
chloric acid;  the  platinichloride  forms  golden-yellow  needles, 
and  the  double  tin  salt,  C7H7NO2.ClH  +  SnCl2,  crystallizes  in 
plates  (Beilstein  and  Wilbrand).  Its  other  compounds  with 
acids  also  crystallize  well. 

Metamidobenzamide,  C6H4(NH2)CO.NH2,  is  obtained,  accord- 
ing to  Chancel,  when  ammonium  sulphide  is  added  to  a  boiling 
aqueous  solution  of  metanitrobenzamide.  It  is  readily  soluble 
in  water,  and  forms  large,  yellow  crystals,  melting  at  750.1  Like 
amidobenzoic  acid  it  is  a  monacid  base. 

Metamidobenzonitril,  C6H4(NH2)CN,  is  formed  when  meta- 
nitrobenzonitril  is  reduced  with  zinc  and  hydrochloric  acid  2  or 
tin  and  acetic  acid,3  as  well  as  by  heating  meta-uramidobenzoic 
acid  with  phosphoric  acid  :  4 

CO—  Ox  /ON 

C6H  /  NH3  =  C6H4  +C02     H20. 


It  crystallizes  from  dilute  alcohol  in  long,  white  needles,  melts 
at  53°  —  54°,  boils  at  288°  —  290°,  and  is  decomposed  by  powerful 
reducing  agents  into  ammonia  and  benzonitril,  the  latter  being 
partially  converted  into  benzylamine.  When  it  is  treated  with 
alcoholic  potash  and  chloroform,  the  carbamine,  CC)H4(NC)CN, 
is  formed  ;  it  has  an  overpowering  odour  and  has  not  been 
further  investigated.  Metamidobenzonitril  is  a  monacid  base 
and  forms  salts  which  crystallize  well. 

Methylmetamidobenzoic  acid,  or  Metabenzosar  cosine,  C6H4(NH. 
CH3)C02H,  was  obtained  by  Griess  as  a  decomposition  product 
of  a-benzocreatine  ;  it  is  slightly  soluble  in  cold,  more  readily  in 
hot  water,  and  crystallizes  in  small  plates. 

Dimethylmetamidobenzoic  acid,  C6H4.N(CH3)2CO2H.  The 
methyl  ether  of  this  acid  is  formed  by  a  molecular  change  from 
the  following  compound,  and  is  a  liquid  which  has  a  faint 
aromatic  odour,  and  boils  at  270°.  The  acid  is  obtained  from  it 
by  decomposition  with  alcoholic  potash,  and  is  also  only  slightly 

1  Beilstein  and  Reichenbach,  Ann.  Chem.  Pharm.  cxxxii.  142. 

2  Hofmann,  Ber.  Deutsch.  Chem.  Ges.  i.  196. 

3  Fricke,  ibid.  vii.  1321. 

4  Griess,  ibid.  viii.  861. 


24fl  AROMATIC  COMPOUNDS. 

soluble  in  hot  water  ;  it  crystallizes  in  dull  needles,  melting  at 
151°. 

Trimethylamidobenzoic  acid,  or  Metabenzoleta'ine,  C7H4N(CH3)3 
O9  +  H2O.  The  iodide  of  this  compound  is  formed  when  a  solu- 
tion of  amidobenzoic  acid  in  methyl  alcohol  is  allowed  to  stand  in 
contact  with  an  excess  of  caustic  potash  and  methyl  iodide  ;  it 
forms  short  prisms  of  the  formula  C7H502N(CH3)3I  +  H2O.  The 
free  base,  which  is  obtained  by  the  action  of  lead  hydroxide, 
crystallizes  in  deliquescent  needles,  which  lose  one  molecule  of 
water  at  105°,  and  have  a  neutral  reaction  and  bitter  taste. 

The  anhydrous  compound  is  converted  on  fusion  into  the 
methyl  ether  of  the  preceding  compound.1 

/C6H4X  C6H4N(CH3)2 

C0<          >N(CH3)3  =  CO 
\  O   / 


/N(C2H30)H 
Acetmetamidobenzoic  acid,  C6H4<(  ,  is    metameric 

\C02H 

with  hippuric  acid  and  is  formed  when  metamidobenzoic  acid  is 
heated  to  160°  with  glacial  acetic  acid.  It  crystallizes  in  fine, 
white  needles,  is  almost  insoluble  in  cold  water,  has  a  bitter 
taste,  at  the  same  time  resembling  that  of  saltpetre,  and  melts  at 
245°;  it  sublimes,  however,  at  a  lower  temperature.2 

2142  Amidobenzoic  acid  percyanide>  (C6H4(NH2)C02H)2C2N2, 
is  the  name  given  by  Griess  to  a  compound  to  which  he  had 
previously  assigned  the  formula  C6H4(NH2)C02HC2N2>  and 
which  is  obtained  by  passing  cyanogen  into  an  aqueous  solution 
of  metamidobenzoic  acid.  It  is  a  yellow,  crystalline  substance, 
which  is  insoluble  in  water,  scarcely  soluble  in  alcohol  and  ether, 
and  has  acid  properties.  On  distillation  it  decomposes  into 
water,  carbon  dioxide,  ammonia,  ammonium  cyanide  and  met- 
amidobenzonitril.  When  heated  to  130°  with  alcohol,  it  decom- 
poses into  metamidobenzoic  acid  and  metabenzamoxalic  acid. 

C6H4.NH.C(NH)C(NH)NH.C6H4 

I  I          +  3H20  = 

C09H  C09H 

CLH4.NH2     *  OJL.NH.CO.CO.OH 

|  '    +   |  +2NH3. 

C02H  C02H 

1  Griess,  Bcr.  Deutsch.  Chcm.  Gcs.  vi.  586. 

2  Forster,  Ann.  Chem.  Pharm.   cxvii.  165  ;  Kaiser,   Ber.  Deutsch.  Chem.  Ges. 
xviii.  2946. 


CYANOCARBOXAMIDOBENZOIC  ACID.  249 

Metalenzamoxalic  acid,  or  Oxalamidobenzoic  acid,  is  also  formed 
by  heating  metamidobenzoic  acid  with  oxalic  acid,  and  crystal- 
lizes from  hot  water  in  narrow  white  plates.1 

Cyanocarbimidobenzoic  acid,  3C9H7N3O2  -f  H2O,  is  formed 
together  with  the  percyanide  according  to  the  equation  : 

.NH2          ON  /NH C=NH 

C6H/  +    |     =  C6H4<;  I 

\C02H       CN  \C02H     CN 

It  is  only  very  slightly  soluble  in  cold  water,  readily  in  hot 
alcohol,  and  crystallizes  in  elliptical  plates,  which  have  an  acid 
reaction  and  combine  with  bases  and  acids. 

Cyanocarloxamidobenzoic  acid,  C9H6NO3,  is  obtained  by  the 
action  of  nitrous  acid  on  a  cold  solution  of  the  preceding  com- 
pound in  hydrochloric  acid  : 


— C=NH 
C6H4<  |  +  HN02  = 

\C09H     CN 

/NH CO 


I  +N 

CN 


It  crystallizes  in  lustrous,  white  plates,  which  have  a  sweet 
taste,  and  are  almost  insoluble  in  cold  water,  but  are  decomposed 
by  boiling  water  with  formation  of  carbon  dioxide,  hydrocyanic 
acid  and  carboxamidobenzoic  acid.  When  it  is  dissolved  in 
ammonia,  uramidobenzoic  acid  is  formed  : 

,NH  -  CO  XNH  -  CO 

C6H4  |       +NH3  =  C6H4<;  |      +HCK 

CN  \C0H     NH 


Methylamine,  ethylamine,  &c.,  act  in  a  similar  manner,  and  a 
large  number  of  substituted  uramidobenzoic  -acids  can,  therefore, 
be  prepared  in  this  way.2 

If  cyanogen  be  passed  into  an  alcoholic  solution  of  metamido- 
benzoic acid,  the  percyanide,  which  has  been  already  mentioned, 

1  Griess,  Ber.  Deutsch.   Chem.  Ges.  i.  191  ;  xi.   1985  ;  xvi.   336  ;  xviii.   2412  ; 
Schiff,  ibid.  xix.  252. 

2  Griess,  ibid,  xviii.  2415. 


250  AROMATIC  COMPOUNDS. 

is  deposited,  and  the  two  following  compounds  crystallize  out 
on  allowing  the  mother  liquor  to  stand  : 

Carbimidamidobenzoic  acid. 

XJ02H 


X2  V 

2C6H4<  +  C2N2  =  >C=NH  +  HON. 

\C02H  /NH/ 

C6H4< 

\C02H 

Ethoxycarbimidamidobenzoic  acid . 

XNH2 

H/          +  C2N24HO.C2H6  = 
XC0H 


h=NH 

C6H/  |  +HCN. 

\rTk  TI     r»r»  TT 

NL-Uojl  UL-oJLJL 


25 


Carbimidamidobenzoic  acid,  or  Guanidodibenzoic  acid,  C15H13 
N304,  is  obtained  from  the  crude  product  by  extraction  with 
boiling  water;  it  separates  out  on  cooling  in  needles,  which 
are  purified  by  being  dissolved  in  hydrochloric  acid,  the  solution 
neutralized  with  ammonia  and  then  precipitated  by  acetic  acid. 
The  precipitate  is  at  first  amorphous,  but  soon  changes  into 
needles.  It  forms  salts  with  both  acids  and  bases.1 

Ethoxycarbimidamido'benzoic  acid,  2C10H12N2O3  +  3H20,  is 
slightly  soluble  in  water,  more  readily  in  alcohol,  and  crystallizes 
in  needles.2 

Meta-uramidolenzoic  acid,  C8H8N203  +  H2O,  is  formed  when 
the  preceding  compound  is  boiled  with  hydrochloric  acid  : 

NH CnzNH  XNH CO 

C6H4<  |  +H20  =  C6H4<  |    +HO.C2H5. 

\C02H     OCH3  \C02H     NH2 

Menschutkin  obtained  it  from  potassium  cyanate  and  met- 
amidobenzoic  acid  hydrochloride,  and  named  it  oxybenzuramic 
acid.3  Griess  then  showed  that  it  is  also  formed  by  bringing 
metamidobenzoic  acid  into  fused  urea.4  It  is  slightly  soluble 
in  water,  more  readily  in  alcohol,  and  crystallizes  in  needles  or 

1  Griess,  Zcitschr.  Chem.  1867,  534. 

2  Journ.  Prakt.  Chem.  [2]  iv.  296. 
8  Ann.  Chem.  Pharm.  cliii.  84. 

4  £er.  Deutsch.  Chem.  Ges.  ii.  47. 


METABENZOGLYCOCYAMINE.  251 

fine  prisms.  Its  salts  have  been  investigated  by  Menschutkin. 
On  treatment  with  concentrated  nitric  acid  it  yields  three  di- 
nitro-compounds  (p.  255). 

Meta-urethanebenzoic  acid,  C10H11NO4,  is  formed  by  the  action 
of  nitrous  acid  on  ethoxycarbimidamidobenzoic  acid1  and  by 
treating  metamidobenzoic  acid  with  ethyl  chlorocarbonate  : 

/NH2          COC1  /NH  -  CO 

C6H4<  +     |          =    C6H4<  |  +  HCL 

\C02H        OC2H5  \C02H    OC2H5 

It  crystallizes  in  plates,  which  are  slightly  soluble  in  water, 
dissolve  in  alcohol  in  every  proportion,  and  melt  at  189°. 

Carboxamidobenzoic  acid,  or  Metacarbamidobenzoic  acid,  C15Hl2 
N2O5,  is  obtained  by  heating  uramidobenzoic  acid  to  200°,  or  by 
repeatedly  evaporating  the  solution  of  its  barium  salt  :  2 

/NH9  /NH.C6H4.C02H 

2CO<  =  C0<  +  CO(NH2)2. 

\NH.C6H4.C02H  \NH.CflH4.C02H 

It  is  also  formed  when  meta-urethanebenzoic  acid  is  heated 
above  its  melting-point,3  and  crystallizes  in  microscopic  needles, 
which  are  insoluble  in  water,  alcohol  and  ether. 

2143  Metabcnzoglycocyamine,  or  Metaguanidobenzoic  acid,  C8H9 
N3O2  +  H2O,  was  first  obtained  by  Griess  by  boiling  amido- 
benzoic  acid  percyanide  with  caustic  potash  solution  ;  it  is  also 
formed  by  the  action  of  ammonia  on  ethoxycarbimidamido- 
benzoic acid,  as  well  as,  similarly  to  glycocyamine  (Part  II.  p.  97), 
by  allowing  an  alcoholic  and  ammoniacal  solution  of  cyanamide 
and  metamidobenzoic  acid  to  stand  :  4 


C6H4.NH2        C=N         C6H4.NH—  C=NH 

I  +1=1  I 

C02H  NH2  C02H         NH2 

It  is  slightly  soluble  in  alcohol,  and  crystallizes  from  hot  water 
in  thin,  four-sided  tablets  which  dissolve  in  caustic  potash,  but 
are  reprecipitated  by  carbon  dioxide.  It  forms  salts  with  the 

1  Griess,  Her.  Deutsch.  Chem.  Ges.  ix.  796. 

Griess,  Zcitschr.  Chem.  1868,  650;  Ann.  Chem.  Pharm.  clxxii.  170. 
3  Wacbendorff,  Ber.  Deutsch.  Chem.  Ges.  xi.  701. 
*  Griess,  ibid.  vii.  575  ;  viii.  323. 


252  AROMATIC  COMPOUNDS. 

mineral  acids,  but  does  not  combine  with  acetic  acid.     On  boil 
ing  with  baryta  water,  uramidobenzoic  acid  is  first  formed  : 

/NH.C(NH)NH2  /NH.CO.NH 


On  continued  boiling,  metamidobenzoic  acid  and  urea  or  de- 
composition products  of  these  are  produced. 

a-Metcibenzocreatine,  2C8H8(CH3)N3O2  +  3H20,  is  formed  by 
the  action  of  methyl  iodide  and  caustic  potash  on  a  solution  of 
the  preceding  compound.  It  is  slightly  soluble  in  water  and 
alcohol,  crystallizes  in  pointed  plates,  and  decomposes  into  urea 
and  benzosarcosine  when  boiled  with  baryta  water. 

ft-Metabenzocreatine  is  prepared  from  ethoxycarbimidamido- 
benzoic  acid  and  methylamine,  and  crystallizes  from  hot  water 
in  small  plates.  On  heating  with  baryta  water  it  yields  meta- 
amidobenzoic  acid,  methylamine,  and  carbon  dioxide  (Griess). 

The  metabenzocreatines,  like  benzoglycocyamine,  exist  in  the 
free  state  as  salts,  and  have  the  following  constitution  : 

0 
C6H4.N  (CH3)  C=N  H          C6H4.NH.C=NH 

CO  -  O  --  NH3  CO—  O—  N(CH3)H2' 

If  these  compounds  be  compared  with  those  of  the  ortho-series, 
it  is  found  that  the  latter  contain  a  molecule  of  water  less  or  are 
anhydro-compounds,  this  class  of  bodies  being  very  readily 
formed  by  and  characteristic  of  the  ortho-series. 

PJienylmetabenzoglycocyamine,  C8H8(C6H5)N3O2  +  H20,is  formed 
when  cyanocarbimidamidobenzoic  acid  is  heated  with  aniline  : 

/NH  -  C=NH 

C6H4<  |  +  H2N.C6H5  = 

\CO2H    CN 

/NH  -  C=NH 
C6H4<  |  +HON. 

\CO2H.   N.C6H5H 

It  is  insoluble  in  alcohol,  but  slightly  soluble  in  hot  water, 
readily  in  hydrochloric  acid  and  caustic  potash,  and  crystallizes 
in  needles  or  plates,  which  have  a  bitter  taste  followed  by  a 
sweet  after-taste. 


PARAMIDOBENZOIC  ACID.  253 

Amidophenylmetabenzoglycocyamine,  G8H8(C6H4.NH2)N8O2,  is 
prepared  in  a  similar  manner  from  paradiamidobenzene ;  it 
crystallizes  in  small  prisms,  and  is  a  diacid  base.1 

2144  Paramidobenzoic  acid  is  obtained  by  the  reduction  of 
paranitrobenzoic  acid  with  ammonium  sulphide,2  or  better  with 
tin  and  hydrochloric  acid.3  It  is  tolerably  soluble  in  water,  very 
readily  in  alcohol,  and  crystallizes  in  long  needles  forming 
fascicular  aggregates ;  it  melts  at  186° — 187°,  and  decomposes 
at  a  higher  temperature  into  carbon  dioxide  and  aniline,  a 
decomposition  which  may  also  be  effected  by  heating  it  to  160° 
— 180°  with  hydrochloric  acid. 

It  is  characteristic  of  paramidobenzoic  acid  that  lead  acetate 
gives  with  its  aqueous  solution  a  crystalline  precipitate  of  the 
double  salt,  C7H4(NH2)02PbC2H302.4 

Paramidobenzoic  acid  hydrochloride,  C7H7NO2.HC1,  crystallizes 
in  small  plates  or  prisms. 

Paramidobenzamide,  C6H4(NH2)CO.NH2,  is  formed  by  the 
reduction  of  paranitrobenzamide  with  ammonium  sulphide,  and 
forms  large,  light  yellow  crystals,  which  melt  at  178° — 179°,  and 
are  much  less  soluble  in  water  than  those  of  the  meta-compound.5 

Paramidobenzonitril,  C6H4(NH2)CN,  may  be  prepared  from 
paranitrobenzonitril,6  and  by  the  distillation  of  para-uramido- 
benzoic  acid  with  phosphorus  pentoxide.7  It  is  readily  soluble 
in  alcohol  and  boiling  water,  and  crystallizes  in  needles,  melting 
at  100°  (Fricke).  It  forms  crystalline  salts  with  acids. 

Dimethylparamidobenzoic  acid,  C6H4N~(CH3)2C02H,  is  obtained 
by  heating  the  amido-acid  with  caustic  potash,  methyl  iodide 
and  wood  spirit.  It  crystallizes  in  short,  broad  needles,  melt- 
ing at  235°,  and  combines  with  acids  and  bases,  but  is  insoluble 
in  acetic  acid.8 

Acetparamidobenzoic  acid,  C6H4(NH.C2H30)CO9H.  Hofmann 
obtained  this  compound  by  the  oxidation  of  acetparatoluide 
with  potassium  permanganate.  It  is  slightly  soluble  in  water, 
readily  in  alcohol,  and  crystallizes  in  needles,  which  melt  with 
decomposition  at  2500.9  On  boiling  with  hydrochloric  acid  it  is 
converted  into  paramidobenzoic  acid.10 

1  Griess,  Ber.  Deutsch.  Chem.  Ges.  xvi.  336. 

2  Fischer,  Ann.  Chem.  Pharm.  cxxvii.  142. 
Beilstein  and  Wilbrand,  ibid,  cxxviii.  264. 
Ladenburg,  Ber.  Dcutsch.  Chem.  Ges.  vi.  130. 

Beilstein  and  Eeichenbach.  Ann.  Chem.  Pharm.  cxxxii.  144. 
Engler,  ibid,  cxlix.  302  ;  Fricke,  Ber.  Deutsch.  Chem.  Ges.  vii.  1322. 
Griess,  ibid.  viii.  861.  8  Michler,  ibid.  ix.  401. 

Ibid.  ix.  401.  10  Kaiser,  ibid,  xviii.  2942. 


254  AROMATIC  COMPOUNDS. 

Para-uramidobenzoic  acid,  CQHBN0Oo,  is  formed  at  the  same 

*  o        o        £       d 

time  as  paracarbamidobenzoic  acid  by  fusing  paramidobenzoic 
acid  with  urea,  or  potassium  cyanate  with  paramidobenzoic  acid 
hydrochloride.  It  forms  elongated  plates,  is  scarcely  soluble  in 
cold,  only  very  slightly  in  boiling  water,  more  readily  in  hot 
alcohol.  Concentrated  nitric  acid  only  forms  one  dinitro-cpm- 
pound. 

Paracarbamidobenzoic  acid,  C15H12N2O5,  is  obtained  by  heating 
the  preceding  compound,  and  forms  small  needles  which  are 
insoluble  in  the  ordinary  solvents. 


CHLORAMIDOBENZOIC  ACIDS,  C6H3C1(NH2)C02H. 


Cl  :  NH2  Melting-point. 

a)     2:5     small,  readily  soluble  needles,1      .    .      212° 
/3)     3:6     long,  almost  insoluble  needles,2    .    .       148° 

8)     3:5     needles,3     . 216° 

e)     4:3     small  needles,4 212° 

2145  The  chloramidobenzoic  acids  corresponding  to  7-  and  f- 
chloronitrobenzoic  acids  are  unknown.  Two  others  have,  how- 
ever, been  prepared,  one  of  which  has  been  obtained  from 
chlorisatin,  and  should  be  identical  with  the  /3-acid,  but  melts 
at  204° ; 5  it  will  subsequently  be  mentioned.  The  second  has 
been  prepared  by  Griess  together  with  the  e-acid  by  decomposing 
metadiazobenzoic  acid  imide,  C6H4N3.C02H,  with  hydrochloric 
acid ;  it  crystallizes  in  small  prisms  and  has  the  constitution 
C1:NH2=2:3.6 

1  Hiibnerand  Biedermann,  Ann.  Chem.  Pharm.  cxlvii.  258  ;  Eack  and  Wilken, 
ibid,  ccxxii.  198. 

2  Cunze  and  Hubner,  ibid,  cxxxv.  Ill  ;  Hiibner  and  Weiss,  Ber.  Dcutsch.  Chem. 
Ges.  vi.  175. 

3  Grube,  ibid.  x.  1703. 

4  Hubner  and  Biedermann ;  Raveill,  Ann.  Chem.  Pharm.  ccxxii.  177. 

5  Dorsch,  Journ.  Prakt.  Chem.  [2]  xxxiii.  50. 

6  Griess,  Ber.  Deutsch.  Chem.  Ges.  xix.  313. 


NITRO-AMIDOBENZOIC  ACIDS.  255 


BROMAMIDOBENZOIC  ACIDS,  C6H3Br(NH2)C02H. 


'O 


Br  :  NH2  Melting-point. 

a)     2:5     broad  needles l 180° 

{¥)     3:6     long,  slightly  soluble  needles  2      .    .       208° 

y)     3:2     needles3 172° 

8)     4:3     light  yellow  needles 4    .     .....       225C 

e)     3:5     colourless,  tough  needles5     ....       215' 


IODAMIDOBENZOIC  ACIDS,  C6H3I(NH2)C02H. 

Melting-point. 
a)     3:2     brown  needles 137° 

/3)     3:6     needles  melting  with  decomposition      209° 

These  have  been  prepared  from  the  iodonitrobenzoic  acids 
and  are  converted  by  reduction  into  orthamidobenzoic  acid. 


NITRO-AMIDOBENZOIC  ACIDS, 
C6H3N02(NH2)C02H. 

2146  Seven  of  the  ten  acids  possessing  this  composition  which 
are  possible  according  to  theory  are  known,  and  their  constitution 
is  shown  on  the  next  page.  The  first  three  have  been  obtained 
from  meta-uramidobenzoic  acid,  which,  as  already  mentioned, 
yields  three  dinitro-compounds.  These  cannot  be  directly  separ- 
ated, but  on  boiling  with  dilute  ammonia  are  converted  into  the 
mononitro-uramidobenzoic  acids,  which  can  be  separated  by 
means  of  their  barium  salts  : 

C  A(N02)2N203  +  H20  =  C8H7(N02)N203+ NO2.OH. 
They  are  re-converted   by  concentrated   nitric    acid   into    the 

1  Burghard,  Ber.  Dcutsch.   Chem.  Gcs.  viii.  560. 

2  Hiibner  and  Meeker,  Zeitschr.  Chem.  1867,  564  ;  Hiibner,  Only  and  Philipp, 
Ann.  Chem.  Pharm.  cxliii.  241  ;  Hiibner  and  Petermann,  ibid,  cxlix.  133. 

8  Ibid.  4  Burghard ;  Raveill. 

5  Hesemann  and  Kohler,  Ann.  Chem.  Pharm.  ccxxii.  169. 


256  AROMATIC  COMPOUNDS. 

dinitro-compounds,  which,  on  boiling  with  water  yield  the  nitro- 
amidobenzoic  acids  : l 

NH.CO.NH,  NH9 

- 


NO, 


C0H2(N02)2<^  =  C6H3(N02)<^  +N20+C!02. 

C02H  CO,H  C02H 

,/^ 

X- 


NO2 
CO2H  C02H          C02H  CO0H 


NH_.KOV          ^o, 

a-Nitro-amidobenzoic  acid  is  slightly  soluble  in  water,  readily 
in  alcohol,  and  crystallizes  in  yellow  needles  or  prisms.2  Nitrous 
acid  converts  it  into  orthonitrobenzoic  acid,  and  on  reduction 
with  tin  and  hydrochloric  acid  it  yields  a-diamidobenzoic  acid. 

fS-Nitro-amidobenzoic  acid  forms  lustrous,  yellowish  red  needles 
or  plates,  which  are  readily  soluble  in  alcohol  and  slightly  in 
water,  and  when  gently  heated  sublime  in  rhombic  plates  with- 
out melting.  Heated  in  a  capillary  tube  it  melts  at  298°  with 
complete  decomposition.3  It  is  converted  by  nitrous  acid  into 
paranitrobenzoic  acid,  and  by  tin  and  hydrochloric  acid  into 
/3-diamidobenzoic  acid. 

y-Nitro-amidobenzoic  acid  crystallizes  in  thick,  golden  yellow 
needles  or  prisms,  which  melt  at  156° — 157°,4  and  dissolve 
readily  in  alcohol  and  hot  water.  Nitrous  acid  converts  it  into 
orthonitrobenzoic  acid,  and  reducing  agents  into  7-diamido- 
benzoic  acid. 

^-Nitro-amidobenzoic  acid  was  obtained  by  Griess  from  dinitro- 
para-uramidobenzoic  acid,5  and  by  Salkowski  by  heating  nitro- 
anisic  acid,  C6H3NO2(OCH3)CO2H,  with   ammonia  to  140°- 
1700.6    It  crystallizes  in  small,  yellow  needles,  which  are  scarcely 
soluble  in  water,  only  slightly  in  boiling  alcohol,  and  melt  at 

Griess,  Per.  Deutsch.  Chem.  Gcs.  ii.  434  ;  v.  192  ;  xi.  1733. 

Journ.  Prakt.  Chem.  [2]  v.  235. 

Kaiser,  Ber.  Deutsch.  Chem.  Ges.  xviii.  2947. 

Ibid,  xviii.  2951. 

Loc.  cit. 

Ann.  Chem.  Pharm.  clxxiii.  52. 


DINITBO-AMIDOBENZOIC  ACIDS.  257 

284°.  It  is  converted  by  the  diazo-reaction  into  metanitrobenzoic 
acid,  and  by  reduction  into  /S-diamidobenzoic  acid. 

e-Nitro-amidobenzoic  acid  was  prepared  by  Griess  from  dinitro- 
ortho-uramidobenzoic  acid,  and  by  Hiibner  from  the  nitrosalicylic 
acid  which  melts  at  228°  by  heating  the  ethyl  ether  with 
alcoholic  ammonia;  e-nitro-amidobenzamide,  C6H3N02(NH2)CO. 
NH2,  is  thus  obtained,  and  crystallizes  in  small,  yellow  needles, 
melting  at  140° ;  it  is  converted  into  the  acid  by  boiling  with 
baryta  water.1  Khalis  obtained  it,  together  with  paranitraniline, 
by  heating  the  nitrobromobenzoic  acid  which  melts  at  179° — 
180°  with  ammonia.2  It  crystallizes  from  hot  water  in  long, 
lustrous,  yellow  needles,  melting  at  270°.  Ethyl  nitrite  con- 
verts it  into  metanitrobenzoic  acid,  and  on  reduction  it  yields 
a-diamidobenzoic  acid. 

%-Nitro-amidobenzoic  acid.  Hiibner  obtained  the  amide  of 
this  acid  from  the  nitrosalicylic  acid  which  melts  at  144°;  it 
crystallizes  in  yellow  plates,  melting  at  109°,  and  on  boiling  with 
baryta  water  yields  the  acid,  which  is  readily  soluble  in  alcohol 
and  crystallizes  from  hot  water  in  long,  yellow,  silky  needles, 
melting  at  204°.  Nitrous  acid  converts  it  into  metanitrobenzoic 
acid. 

rj-Nitro-amidobenzoic  acid  is  formed  by  the  reduction  of 
S-dinitrobenzoic  acid  with  ammonium  sulphide,3  and  crystallizes 
from  water  in  long, golden  yellow  needles,  or  small,  compact  prisms, 
melting  at  208°.  It  is  converted  into  metanitrobenzoic  acid  by 
ethyl  nitrite,  while  metachlorobenzoic  acid  may  be  obtained  from 
it  by  replacing  the  amido-group  by  chlorine  and  the  nitroxyl  by 
hydrogen ;  its  constitution  is  thus  established. 


DINITRO-AMIDOBENZOIC    ACIDS, 


2147  Dinitro-orthamidobenzoic  acid  or  Dinitro-anthranilic  acid 
(NO2:NO2  =  3  :.5)  is  prepared  by  the  action  of  ammonia  on 
the  ether  of  dinitrosalicylic  acid.  It  is  slightly  soluble  in 
alcohol,  and  crystallizes  from  it  in  lustrous,  golden  scales,  melting 
at  2560.4 

1  Ann.  Chem.  Pharm.  xix.  21.  2  Ibid,  cxcviii.  112. 

3  Bocker,  Grube  and  Kollwage,  Bcr.  Deutsch.  Chem.  Ges.  x.  1703  ;  Ann.  Chem. 
Pharm.  ccxxii.  81. 

4  Salkowski,  Ann.  Chem.  Pharm.  clxxiii.  40. 


258  AROMATIC  COMPOUNDS. 

Dinitroparamidobenzoic  acid,  (NO2  :  NO2  =  2  :  G).  Cahours,  in 
1  849,  found  that  an  acid  soluble  in  ammonia  is  formed  by  the 
action  of  fuming  nitric  acid  on  nitranisic  acid,  in  addition  to 
dinitro-anisol  and  trinitro-anisol  (Part  III.,  p.  125).  This  sub- 
stance being  of  a  splendid  golden  yellow  colour,  he  named 
it  chrysanisic  acid,  C7H5N307,  looking  upon  it  as  a  homologue 
of  picric  acid.1  After  trinitrocresol  had  been  prepared,  Kolbe 
suggested  that  it  is  identical  with  chrysanisic  acid,2  but  Beilstein 
and  Kellner  showed  that  this  is  not  the  case,  since  the  latter  has 
the  formula  C7H5N306,  and  differs  from  the  isomeric  trinitro- 
toluene, which  was  prepared  and  described  by  Wilbrand.3 

The  actual  constitution  of  chrysanisic  acid  was  determined 
by  Salkowski,  who  found  that  it  is  not  contained  in  the  product  of 
the  action  of  nitric  acid  on  nitranisic  acid,  but  is  formed  by  the 
action  of  ammonia  on  dinitro-anisic  acid  :  4 


C6H2(OCH3)(N  O^COjH  +  NH3  =  C6H2(NH2)(NO2)2CO2H  + 

HO.CH3. 

It  may  also  be  obtained  by  the  oxidation  of  dinitropara- 
toluidine,5  and  crystallizes  froni  hot  water,  in  which  it  is  only 
very  slightly  soluble,  in  fine  needles,  and  from  alcohol  in  lustrous, 
golden,  rhombic  plates,  melting  at  259°.  On  heating  to  200°— 
210°  with  fuming  hydrochloric  acid,  /3-trichlorobenzoic  acid  is 
formed,  and  with  nitric  acid  it  yields  picric  acid,  while  the 
dinitro-anisic  acid  from  which  it  is  prepared  is  converted  into 
/3-dinitrophenol  when  heated  with  water  to  1700.6 


DIAMIDOBENZOIC  ACIDS,  C6H3(NH2)2C02H. 

2148  The  formation  of  these  has  been  already  mentioned 
under  the  dinitro-  and  nitro-amido-benzoic  acids.  The  numbers 
signify  the  position  of  the  amido  groups. 

a-Diamidobenzoic  acid  (2  :  5)  is  slightly  soluble  in  alcohol  and 
hot  water,  and  crystallizes  in  very  small  prisms,  which  decompose 
on  heating  with  formation  of  paradiamidobenzene. 

Ann.  Chim.  Phys.  [3]  xxvii.  454. 

Lehrb.  Org.  Chcm.  ii.  145. 

Ann.  Chcm.  Pharm.  cxxviii.  164. 

Ibid,  clxiii.  1. 

Friederici,  Bcr.  Deutsch.  Chem.  Ges.  xi.  1975. 

Salkowski  and  Paidolph,  ibid.  x.  1254. 


DIAMIDOBENZOIC  ACIDS.  259 

(S-Diamidobenzoic  acid  (3  : 4)  crystallizes  from  hot  water  in 
small  plates,  which  melt  at  211°,  and  decompose  at  a  higher 
temperature,  more  easily  when  mixed  with  powdered  glass  or 
lime,  into  carbon  dioxide  and  orthodiamidobenzene. 

y-Diamidobenzoic  acid  (2:3)  forms  long,  yellowish  white 
needles,  and  also  yields  orthodiamidobenzene  on  heating. 

S-Diamidobenzoic  acid  (3  :  5)  is  slightly  soluble  in  water,  more 
readily  in  alcohol,  and  crystallizes  in  long  needles  which  melt  at 
228°  when  gradually  heated,  but  at  236°  when  rapidly  heated,1 
and  are  carbonized  at  a  higher  temperature  with  evolution  of 
ammonia.  On  heating  with  caustic  baryta,  it  decomposes  into 
carbon  dioxide  and  metadiamidobenzene.  It  decomposes  car- 
bonates and  forms  salts  which  crystallize  well.  Its  dilute 
aqueous  solution  is  coloured  deep  yellow  by  nitrous  acid 
(p.  263). 

Barium  diamidobenzoate,  2(C6H3(NH2)2CO2)2Ba  {-  3H2O,  cry- 
stallizes in  yellowish  prisms,  which  are  readily  soluble  in  water. 
Like  its  isomerides,  it  also  combines  with  acids. 

S-Diamidobenzoic  acid  hydrochloride,  C6H3(CO2H)(NH2)2 
(C1H)2,  is  readily  soluble  in  water,  but  only  slightly  in  hydro- 
chloric acid,  and  crystallizes  in  needles. 

S-Diamidobenzoic  acid  sulphate,  (C6H3(CO2H)(NH2)2)SO4H2, 
forms  white  needles  or  prisms,  which  are  slightly  soluble  in  water 
and  still  less  so  in  alcohol.2 

Hexmethyl-§-diamidobenzoic  acid,  or,  as  Griess  called  it,  six- 
fold methylated  diamidobenzoic  acid,  is  not  an  acid  in  its 
properties  but  a  strongly  alkaline  ammonium  hydroxide  and,  at 
the  same  time,  a  salt.  The  iodide  is  formed  by  the  action  of 
methyl  iodide  and  caustic  potash  on  a  solution  of  3-diamido- 
benzoic  acid  in  methyl  alcohol.  It  crystallizes  in  six-sided 
tablets  or  plates,  and  when  treated  in  concentrated  aqueous 
solution  with  silver  oxide  yields  the  free  base  : 

N(CH3)3 
/N(CH3)3I 

C6H  /  CO.OH    +  Ag20  =  C6H3f  CO.O  +  2AgI. 

\N(CH3)3I  \N(CH3)3OH 

It  is  obtained  on  evaporation  as  a  crystalline  mass,  which 
consists  of  small  plates,  is  very  hygroscopic  and  behaves  like 

1  Hiibner,  Ann.  Chem.  Pharm.  ccxxii.  85. 

2  Griess,  ibid.  cliv.  328. 


260  AROMATIC  COMPOUNDS. 

caustic  potash.  The  carbonate  crystallizes  from  alcohol  in 
small  plates,  is  readily  soluble  in  water  and  has  an  alkaline 
reaction.1 


TRI-AMIDOBENZOIC  ACID,  C6H2(NH2)3CO2H. 

Salkovvski  obtained  this  compound  by  the  reduction  of 
chrysanisic  acid  with  tin  and  hydrochloric  acid.  It  crystal- 
lizes from  boiling  water  in  fine,  lustrous  needles,  and  decom- 
poses on  heating  into  carbon  dioxide  and  triamidobenzene.  Its 
solution  has  an  acid  reaction,  and  it  is  at  once  a  monobasic 
acid  and  a  diacid  base. 


DIAZO-DERIVATIVES  OF   BENZOIC  ACID. 

2149  The  amidobenzoic  acids  behave  in  some  respects  like 
amido-acetic  acid  and  its  homologues,  and  in  others  like  aniline, 
since  they  can  be  easily  converted  into  diazobenzoic  acids. 
For  this  purpose,  a  magma  of  amidobenzoic  acid  and  nitric 
acid  is  well  cooled  by  ice  and  saturated  with  nitrogen  trioxide, 
the  nitrate  formed  being  then  precipitated  with  alcohol  and 
ether.  Other  salts  are  obtained  in  a  similar  manner.  The 
sulphates  are  best  prepared  by  dissolving  the  nitrate  in  a  cold 
mixture  of  equal  parts  of  water  and  sulphuric  acid,  and  precipitat- 
ing in  crystals  by  the  addition  of  strong  alcohol  and  then  ether.2 
The  diazobenzoic  acids,  which,  like  the  diazophenols,  only  exist  as 
anhydrides,  are  obtained  from  these  salts  by  the  action  of  caustic 
potash.  They  also  form  double  salts,  which  Griess  looks  upon 
as  basic  salts  : 

Diazobenzoic  acid.  Diazobenzoic  acid  nitrate. 

Nz=N  /N=N.NO3 

|  C6H4< 

CO-O  \CO.OH. 

Diazobenzoic  acid  seminitrate. 

xNzzN.O.CO.C6H4 

C6H/  | 

NJO.OH        N=N.NO3. 

1  Griess,  Ber.  Deutsch.  Chem.  Ges.  vii.  39 ;  Briihl,  ibid.  viii.  485. 

2  Griess,  ibid,  xviii.  960. 


DIAZO-DERIVATIVES.  261 

The  substituted  amidobenzoic  acids,  as  well  as  their  amides, 
uitrils,  &c.,  also  form  diazo-compounds. 

Orthodiazdbenzoic  acid  nitrate,  NO3.N2.C6H4.CO2H,  is  readily 
soluble  in  water,  and  crystallizes  in  rhombic  or  six-sided  tablets, 
or  prisms,  which  explode  violently  on  heating.  When  it  is  re- 
peatedly dissolved  in  water  and  precipitated  with  alcohol  and 
ether,  or  when  an  alcoholic  solution  of  anthranilic  acid  is  treated 
with  nitrogen  trioxide,  orthodiazobenzoic  acid  seminitrate,  NO3.N2. 
C6H4.CO2.N2.C6H4.CO2H,  is  formed ;  it  crystallizes  in  long,  white 
needles,  and  detonates  violently  when  heated.1 

Metadiazobenzoic  acid  nitrate  crystallizes  in  prisms,  which  are 
slightly  soluble  in  cold  water.2  On  adding  an  alkali  to  its  solution, 

,N  =  N 
a  precipitate  of  metadiazobenzoic  acid,  C6H4y        .     |  ,  is  thrown 

\CO-0 
down. 

This  forms  a  yellow  mass  which  is  very  unstable. 

Metadiazobenzoic  acid  sulphate,  HSO4.N2.C6H4.CO2H,  forms 
long,  narrow  plates,  which  are  readily  soluble  in  water.  When 
it  is  repeatedly  precipitated  from  aqueous  solution  by  the 
addition  of  alcohol  and  ether,  it  becomes  converted  into  the 
basic  salt,  to  which  Griess  has  given  the  formula  5C7H4N2O2, 
2SO4H2.3  According  to  Beilstein  it  is  probably  2(C7H5N2O2)2 
SO4  +  C7H5N2O2(OH).4  It  crystallizes  in  small  needles. 

When  the  normal  sulphate  is  heated,  it  decomposes  with  a 
violent  evolution  of  gas  and  formation  of  free  sulphuric  acid, 
sulphoxybenzoic  acid,  and  a  very  stable  compound,  CUH10SO8,5 
which  probably  has  the  following  constitution :  S02(C6H3(OH) 
C02H)2. 

Metadiazobenzoic  acid  platinichloride,  (C7H5N2O2)2PtCl6,  is 
obtained  by  the  addition  of  platinum  chloride  to  a  solution  of 
the  nitrate  ;  it  crystallizes  in  yellow  prisms. 

Metadiazobenzoic  acid  perbromide,  Br2N — BrN.C6H4.CO2H,  is 
precipitated  as  an  oil  by  the  addition  of  a  solution  of  bromine 
in  hydrobromic  acid  to  a  solution  of  the  nitrate ;  it  soon  solidifies 
to  a  mass  of  yellow  prisms,  and  is  converted  by  ammonia  into 
diazobenzoic  acid  imide. 

Metadiazobenzamide  nitrate,  NO3.N2.C6H4.CO.NH2,  crystallizes 
in  white,  explosive  needles. 

1  Griess,  Ann.  Chem.  Pharm.  cxvii.  39,  cxxxv.  121  ;  Bcr.  Deutsch.  Chem.  Gcs. 
ix.  1653.  a  Griess,  Ann.  Chem.  Pharm.  cxx.  126. 

3  Ber.  Deutsch.  Chem.  Ges.  ix.  1655. 

4  Haiulb.  Org.  Chem.  1139.  5  Jahresb.  Chem.  1864,  351. 

248 


21)2  AROMATIC  COMPOUNDS. 

Metadiazobenzonitril  nitrate,  NO3.N2.C6H4.CN,  forms  explosive 
needles  or  prisms  which  are  only  slightly  soluble  in  cold  water.1 

Paradiazobenzoic  acid  nitrate  also  crystallizes  in  white,  explosive 
prisms.2 

/N*\ 

Nitrodiazobenzoic  acid,  C6H3(NO2)<^          V),  is  formed  when 


S-nitro-amidobenzoic  acid  is  brought  into  absolute  alcohol  nearly 
saturated  with  nitrogen  trioxide  ;  it  forms  light  yellow,  explosive 
plates.3 

Diazobenzene-amidobenzoic  acid,  C6H5.N=N.NH.C6H4.CO2H, 
is  obtained  by  mixing  aqueous  solutions  of  diazobenzene  nitrate 
and  metamidobenzoic  acid.4  According  to  Griess,  this  compound 
is  identical  with  that  obtained  by  the  action  of  aniline 
on  metadiazobenzoic  acid,  and  which  was  therefore  considered 
to  have  the  constitution  C6H6.NH.N=N.C6H4.CO2H.  Griess, 
however,  expresses  the  constitution  of  both  compounds  by  the 
same  formula,  C6H5.NH=NH=NH.C6H4.CO2H  (Part  III, 
p.  269).5 

By  either  process,  a  yellow,  crystalline  substance  is  obtained, 
which  separates  from  ether  in  small  plates,  and  is  decomposed 
by  hydrochloric  acid  with  formation  of  metamidobenzoic  acid, 
metachlorobenzoic  acid,  metahydroxybenzoic  acid,  aniline,  phenol 
and  nitrogen.  The  acid  forms  a  yellow  solution  in  alkalis  ;  on 
the  addition  of  barium  chloride  to  its  ammoniacal  solution,  which 
must  not  be  too  dilute,  the  barium  salt  separates  out  in  small, 
light  yellow  crystals. 


is  formed  by  the  action  of  metamidobenzoic  acid  on  metadiazo- 
benzoic acid,6  and  therefore  as  an  intermediate  product  when 
nitrogen  trioxide  is  passed  into  an  alcoholic  solution  of  metamido- 
benzoic acid.7  It  forms  orange-yellow,  crystalline  granules,  which 
are  almost  insoluble  in  water,  alcohol,  ether,  &c.,  and  detonate 
at  180°.  It  is  soluble  in  alkalis,  and  is  reprecipitated  by 
acids,  even  acetic  acid.  On  boiling  with  hydrochloric  acid, 
it  decomposes  with  evolution  of  nitrogen  into  metamidobenzoic 
acid  and  metachlorobenzoic  acid.  It  is  a  tolerably  strong  dibasic 
acid  and  decomposes  carbonates. 

1  Griess,  Bcr.  Deuisch.  Chem.  Ges.  ii.  370. 

2  Jahresb.  Chem.  1864,  353. 

3  Salkowski,  Ann.  Chem.  Pliarm.  clxxiii.  63. 

4  Griess,  ibid,  cxxxvii.  63.  5  Bcr.  Deutsch.  Chem.  Ges.  vii.  1619. 
6  Jahreab.  Chem.  1864,  353.                7  Ann.  Chem.  Pharm.  cxvii.  1. 


DIAMIDOBENZOIC  ACIDS.  263 

Paradiazo-amidobenzoic  acid  was  obtained  by  Beilstein  and 
Wilbrand  by  treating  a  saturated  alcoholic  solution  of  paramido- 
benzoic  acid  with  a  solution  of  nitrogen  trioxide  in  alcohol.  It 
is  an  orange-yellow,  crystalline  powder,  which  is  only  slightly 
soluble  in  boiling  alcohol.1 

Isomeric  compounds  are  formed  from  metadiazobenzoic  acid 
and  paramidobenzoic  acid,  and  from  paradiazobenzoic  acid  and 
metamidobenzoic  acid  (Griess). 

2150  The  Action  of  Nitrous  Acid  on  the  Diamidobenzoic  Acids. 
When  sodium  nitrite  is  added  to  a  neutral  solution  of  a-diamido- 
benzoic  acid,  which  contains  the  amido-group  in  the  para-position, 
paramidodiazobenzoic  acid  is  formed  : 


/NH 

+  NO.H-QA 

.OH 


NO2H  =  C6H3— N=N  +  2H2O. 


CO—  O 

It  is  insoluble  in  ether,  slightly  soluble  in  hot  alcohol,  readily 
in  hot  water,  and  crystallizes  in  fine  needles  or  four-sided  plates, 
which  are  brass  coloured,  have  a  very  bitter  taste,  and  detonate 
on  heating.  It  does  not  combine  with  bases,  but  forms  crystal- 
line salts  with  acids  ;  it  also  combines  with  amido-bases  and 
phenols  to  form  azo-compounds.2 

Nitrous  acid  acts  upon  the  two  orthodiamidobenzoic  acids 
(/5  and  7)  in  the  following  manner  : 


/NH\ 

,2     +  N02H  =  C6H3f-N  =  N  +  2H20. 
'\COOH  \CO.OH 


The  diazo-imidobenzoic  acids  obtained  in  this  manner  crystal- 
lize in  needles  and  are  powerful  acids,  the  barium  salts  of  which 
are  only  slightly  soluble  in  cold  water.3 

Metadiamidobenzoic  acid  corresponds  exactly  with  metadi- 
amidobenzene  in  its  behaviour  towards  nitrous  acid.  In  a 
very  dilute  solution  a  yellow  colouration,  is  produced,  and  this 
reaction  is  so  delicate  that  one  part  of  nitrous  acid  can 
be  detected  in  five  million  parts  of  water.  In  concentrated 

1  Ann.  Chem.  Pharm.  cxxviii.  269. 

2  Griess,  Ber.  Deutsch.  Chem.  Ges.  v.  200,  xvii.  603. 

3  Griess,  ibid.  ii.  436. 


264  AROMATIC  COMPOUNDS. 

solutions  a  reddish-brown  precipitate  of  triamido-azobenzoic  acid  is 
formed  : 

/NH2  /NH2  /NH2 

2C6H3^-NH2    +N02H=C6H3f-N=N-C6H2^NH2    +2KLO. 

\CO.OH  \CO.OH  \CO.OH 

This  substance  is  soluble  in  alkalis,  and  is  reprecipitated  by 
acids.1 

/NILNH, 
HYDRAZINEBENZOIC  ACIDS,  C6H4< 

\OO.OH. 

2151  These  compounds  are  obtained  from  the  amidobenzoic 
acids  by  the  methods  which  are  employed  in  the  preparation  of 
phenylhydrazine  from  aniline  (Part  III.,  p.  275). 

Orthohydrazinebenzoic  acid  is  slightly  soluble  in  alcohol  and 
ether,  and  crystallizes  from  hot  water  in  fine  needles.  It  reduces 
Fehling's  solution  and  salts  of  silver  and  mercury  in  the  cold, 
and  combines  with  bases  and  acids.  When  it  is  gently  heated 
with  concentrated  hydrochloric  acid  or  heated  rapidly  to 
220°  —  230°  in  a  stream  of  carbon  dioxide,  the  anhydride  is 
formed. 

/NH\ 
Orthobenzoylhydrazide,  C6H4<^          />NH,  forms  crystals  which 

MXK 

are  slightly  soluble  in  alcohol,  ether,  and  hot  water,  have  an  acid 
reaction,  and  are  readily  dissolved  by  alkalis.  It  does  not  com- 
bine with  acids,  and  does  not  reduce  salts  of  mercury  or  Fehling's 
solution,  but  causes  a  precipitation  of  silver  from  an  ammoniacal 
solution.2 

Metahydrazinebenzoic  acid  is  insoluble  in  ether,  slightly  soluble 
in  alcohol  and  hot  water,  and  crystallizes  in  small,  yellowish 
plates,  which  melt  with  decomposition  at  186°.  It  has  an  acid 
reaction,  combines  with  acids  and  bases,  and  reduces  Fehling's 
solution.  Nitrous  acid  converts  it  into  the  imide  of  metadiazo- 
benzoic  acid  : 

/C02H  /CO2H 


1  Voit,  Ann.   Chem.  Pharm.  xcix.  100  ;  Griess,  ibid.  cliv.  334 ;  Ber.  Deutsch. 
Chem.  Qes.  xvii.  606. 

2  Fischer,  Ber.  Deutsch.  Chem.  Qes.  xiii.  679. 


AZO-DERIVATIVES  OF  BENZOIC  ACID.  265 

This  is  a  monobasic  acid,  which  is  scarcely  soluble  in  cold, 
slightly  in  hot  water,  and  readily  in  alcohol ;  it  crystallizes  in  thin 
plates,  melting  at  160°.  Metahydrazinebenzoic  acid  is  decom- 
posed in  presence  of  diazobeuzene  nitrate  with  formation  of 
diazobenzoic  acid  imide,  metamidobenzoic  acid,  diazobenzene- 
imide  and  aniline.1 


AZO-DERIVATIVES  OF  BENZOIC  ACID. 

2152  These  are  formed,  like  other  azo-compounds,  by  the 
reduction  of  the  corresponding  nitro-derivatives,  the  following 
substances  being  obtained : 

Azoxybenzoic  acids.  Azobenzoic  acids.  Hydrazobenzoic  acids. 

.N.CeH^COjjH         N.C6H4.C02H         HN.C6H4.C02H 
XN.C6H4.C02H         N.C6H4.C02H        HN.C6H4.CO2H. 

Ortho-azoxylenzoic  add.  Griess  prepared  this  body  by  heating 
equal  parts  of  orthonitrobenzoic  acid  and  caustic  potash  with 
alcohol.2  It  may  also  be  obtained,  together  with  orthonitro- 
toluene,  by  boiling  orthonitrobenzyl  alcohol  with  caustic  potash.3 
It  is  only  slightly  soluble  in  water,  and  crystallizes  from  hot 
alcohol  in  small,  white,  rhombic  prisms,  which  decompose  on 
fusion.  The  barium  salt  is  readily  soluble  in  water  and  forms 
pointed  crystals. 

Ortho-azobenzoic  acid  is  formed  by  the  action  of  sodium 
amalgam  on  a  solution  of  sodium  orthonitrobenzoate.  It  is 
almost  insoluble  in  water  and  crystallizes  from  hot  alcohol 
in  fine,  dark-yellow  needles,  which  melt  at  237°  with  partial 
decomposition.  Its  yellow  barium  salt  crystallizes  with  seven 
molecules  of  water  in  prisms,  or  with  nine  molecules  in 
needles.4 

Orthohydrazobenzoic  acid  is  obtained  by  treating  a  concentrated 
alkaline  solution  of  azoxybenzoic  acid  with  sodium  amalgam.5 
It  crystallizes  from  alcohol  in  colourless,  elliptical  plates  or 

Griess,  Ann.  Chem.  Pharm.  ix.  1657  ;  Fischer,  ibid.  xvi.  1335. 

Ibid.  vii.  1611. 

Jaffe,  Hoppe-Seyler's  Zeitschr.  ii.  57. 

Griess,  Ber.  Deutsch.  Chem.  Ges.  x.  1869. 

Griess,  ibid.  vii.  1612. 


266  AROMATIC  COMPOUNDS. 

microscopic  prisms,  and  is  readily  oxidized  to  the  preceding 
compound. 

Metazoxylenzoic  acid  is  insoluble  in  water,  slightly  soluble  in 
alcohol  and  ether,  and  forms  microscopic  needles  or  plates.  Its 
barium  salt  is  an  almost  insoluble  precipitate.1 

Metazobenzoic  acid  was  first  prepared  by  Neubauer  by  the 
oxidation  of  metamidobenzoic  acid  with  potassium  perman- 
ganate, bat  was  not  further  investigated.2  Beilstein  and  Wil- 
brand  then  found  that  an  acid  is  formed  by  the  action  of  zinc 
on  an  alkaline  solution  of  metanitrobenzoic  acid,  which,  according 
to  its  composition,  lies  between  nitro-  and  amido-benzoic  acids.3 
Strecker,  who  prepared  it  by  means  of  sodium  amalgam, 
named  it  azobenzoic  acid.4  It  is  also  formed  by  the  action  of 
zinc  on  ammonium  metanitrobenzoate.5  Acids  separate  it  from 
its  salts  as  a  light-yellow,  viscid  precipitate,  which  becomes 
granular  when  heated  with  alcohol,  and  is  only  slightly  soluble 
in  water,  alcohol,  and  ether.  Its  almost  insoluble  barium  salt 
crystallizes  in  microscopic,  rhombic  plates  containing  five  mole- 
cules of  water. 

On  distillation  with  lime,  azophenylene,  C12H8~N"2,  is  formed, 
while  its  copper  salt  yields  azobenzene  on  dry  distillation.6 

Metahydrazdbenzoic  acid  was  obtained  by  Strecker  by  adding 
ferrous  sulphate  and  then  hydrochloric  acid  to  an  alkaline 
solution  of  the  azo-acid.  It  is  also  formed  by  the  continued 
action  of  sodium  amalgam  and  other  reducing  agents.  It  is 
amorphous,  insoluble  in  water,  and  only  slightly  soluble  in 
alcohol.  It  is  readily  oxidized  in  alkaline  solution  to  the 
preceding  compound  and,  like  hydrazobenzene,  undergoes  an 
intermolecular  change  (Part  III.,  p.  295),  when  it  is  boiled 
with  concentrated  hydrochloric  acid,  diamidodiphenic  acid, 
C12H6(NH2)2(C02H)2,  being  formed.7 

Parazobenzoic  acid  is  almost  insoluble  in  alcohol,  water  and 
ether,  and  forms  a  yellow  or  reddish  precipitate,  which  becomes 
granular  on  boiling  and  melts  at  about  240°. 8  The  barium  salt 
is  a  flesh-coloured  precipitate ;  azophenylene  is  formed  when 
the  calcium  salt  is  distilled  (Glaus). 

Parahydrazobenzoic  acid  is  insoluble  in  water  and  crystallizes 

1  Griess,  Jahrcsber.  1864,  352.  2  Ann.  Chem.  Pharm.  cvi.  70. 

8  Ibid,  cxxviii.  267.  *  Ibid,  cxxix.  129. 

6  Sokolow,  Journ.  Prakt.  Chem.  xciii.  425  ;  Liebert,  ibid,  xciii.  429. 

6  Claus,  Ber.  Deutsch.  Chem.  Ges.  viii.  41. 

7  Griess,  ibid.  vii.  1609  ;  Schultz,  Ann.  Chem.  Pharm.  cxcvi.  18. 

8  Reichenbach  and  Beilstein,  Ann.  Chem.  Pharm.  cxxix.  144  ;  Bilfinger,  ibid. 
cxxxv.  154. 


DIAZOXYBENZOIC  ACID.  267 

from  alcohol  in  needles;   its  alkaline  solution  absorbs  oxygen 
with  formation  of  the  azo-acid. 

/N\ 

Diazoxylcnzoic    acid,    0<     |    )C6H3.CO2H.     When   8-dinitro- 


oenzoic  acid  is  dissolved  in  caustic  soda  and  treated  with  sodium 
amalgam,  the  liquid  becomes  coloured  black  but  remains  perfectly 
clear,  appearing  brown  when  diluted.  Acids  added  to  this  solu- 
tion precipitate  diazoxybenzoic  acid  as  an  amorphous,  black 
powder,  which  is  insoluble  in  water,  alcohol,  ether,  &c.,  and 
detonates  feebly  on  heating.  The  alkali  salts  form  black  solu- 
tions in  water  ;  the  salts  of  other  metals  are  black  precipitates. 
The  barium  salt,  when  dried  at  70°,  becomes  so  strongly  electrified 
that  the  particles  continue  in  motion  for  hours;  it  loses  this 
property  at  a  higher  temperature.  Tin  and  hydrochloric  acid 
reduce  the  acid  to  S-diamidobenzoic  acid. 

Isodiazoxybcnzoic  acid  is  obtained  from  /3-dinitrobenzoic  acid 
and  resembles  the  preceding  compound,  but  is  not  attacked  by 
tin  and  hydrochloric  acid.1 

Azonitromethanebenzoic  acid,  N02.CH2N:=NC6H4.CO2H,  is 
formed  when  an  aqueous  solution  of  pure  metadiazobenzoic 
acid  nitrate  is  mixed  with  a  dilute  solution  of  nitromethane 
in  caustic  potash,  and  the  whole  treated  with  an  excess  of 
hydrochloric  acid  after  standing  for  some  time.  It  is  readily 
soluble  in  hot  alcohol  and  ether,  slightly  in  boiling  water, 
and  crystallizes  in  stellate  groups  of  yellowish-red  plates, 
which  are  almost  tasteless  and  detonate  on  heating.  Silver 
nitrate  added  to  its  ammoniacal  solution  produces  a  deep  red 
precipitate.2 

N.C6H4.C02H 

Azo-aceto-acetic  lenzoic  acid,  \\  ,  is  obtained 

N.CH(CO.CH3)C02H 

by  the  action  of  metadiazobenzoic  acid  sulphate  on  aceto-acetic 
ether,  the  method  described  for  the  preparation  of  the  preceding 
compound  being  followed.  It  is  thrown  down  by  hydrochloric 
acid  as  a  light  yellow  precipitate  consisting  of  microscopic 
spheres,  and  is  insoluble  in  boiling  water,  crystallizing  from  hot 
alcohol  in  narrow  plates  or  small  needles,  which  have  a  bitter 
taste.  On  careful  heating  it  fuses  to  an  oil,  which  solidifies  on 
cooling  to  a  waxy  mass,  but  at  a  higher  temperature  it  detonates 

1  Meyer  and  Michler,   Ann.    Chem.  Pharm.  clxxv.  152  ;  Ber.  Deutsch.  Chem. 
Ges.  vi.  746,  vii.  422. 

2  Griess,  ibid,  xviii.  961. 


268  AEOMATIC  COMPOUNDS. 

feebly,  a  large  quantity  of  carbon  separating  out.  Its  silver  salt 
is  a  light  yellow,  amorphous  precipitate. 

NC6H4.C02H 
Azomalonic-benzoic  acid,    \  .     Griess  obtained  this 

NCH(C02H)2 

compound  in  a  similar  manner  from  malonic  ether.  Hydrochloric 
acid  separates  it  from  the  product  as  an  amorphous,  fiery  yellowish 
red  precipitate,  which  crystallizes  from  hot  alcohol  in  microscopic 
plates.  On  heating  it  froths  up  and  chars. 


XS03H 
MONOSULPHOBENZOIC  ACIDS,  C6H4< 

\COOH. 

2153  OrthosulpJiobenzoic  acid  is  formed,  together  with  ortho- 
sulphamidobenzoic  acid,  when  orthotoluenesulphamide  is  oxidized 
with  potassium  permanganate.  On  the  addition  of  hydrochloric 
acid  to  the  nitrate,  the  anhydride  of  the  sulphamide  separates 
out,  while  acid  potassium  orthosulphobenzoate  remains  in  solu- 
tion and  is  deposited  in  large  monoclinic  tablets.1 

It  may  also  be  obtained  by  heating  the  diazo-compound  of 
anthranilic  acid  with  an  alcoholic  solution  of  sulphur  dioxide.2 

It  crystallizes  from  water  in  large,  monoclinic  tablets,  which  do 
not  deliquesce  in  the  air  and  melt  at  240°  with  decomposition. 
On  fusion  with  caustic  potash  salicylic  acid  is  formed.3 

Acid  barium  orthosulpholenzoate,  (C7H5S03)2Ba  -f  2H2O, 
crystallizes  in  needles,  and  is  less  soluble  in  water  than  the 
normal  salt. 

OrthosulpTiamidobenzoic  acid  is  not  known  in  the  free  state,  as 
when  it  is  liberated  from  its  salts  by  the  addition  of  an  acid  it  is 
immediately  converted  into  the  anhydride : 

SO,NH2 

C6H4  =   C6H4<         >NH  +  H,0. 

\CO.OH  ^GQ/ 

This  body  is  slightly  soluble  in  cold,  more  readily  in  hot  water 
and  alcohol,  and  forms  crystals  which  melt  at  220°  and  are 

1  Remsen,    Ann.   Chcm.   Pharm.   clxxviii.    293  ;  Fahlberg  and  Remsen,  Bcr. 
Deutsch.  Chem.  Ges.  xii.  471. 

2  Wiesinger,  ibid.  xii.  1349.  3  Bottinger,  ibid.  viii.  374. 


SACCHARIN.  269 


sweeter  than  sugar.  The  salts,  which  are  readily  soluble  in 
water,  have  also  a  sweet  taste.  When  the  anhydride,  which  is 
called  lenzoylsulphimide,  is  heated  to  150°  with  hydrochloric 
acid,  it  is  converted  into  orthosulphobenzoic  acid.  It  is  not 
attacked  by  phosphorus  pentachloride. 

According  to  Fahlberg  and  List x  it  is  a  powerful  antiseptic, 
and,  since  a  very  dilute  solution  of  it  is  as  sweet  as  a  concen- 
trated solution  of  cane  sugar,  they  believe  that  it  may  find  an 
extended  application.  It  could  thus  be  used  as  a  sweetening 
agent  in  the  diet  of  patients  suffering  from  diabetes  and  in 
many  other  cases  as  a  cheap  substitute  for  sugar.  They  propose 
for  it  the  unsuitable  name  of  saccharin,  which  has  also  been 
given  (Part  II.,  p.  547)  to  the  lactone  of  saccharic  acid. 

2154  Metasulphobenzoic  acid.  In  1834  Mitscherlich  found 
that  benzoic  acid  combines  with  anhydrous  sulphuric  acid,  SO3, 
to  form  an  acid  which  can  be  heated  to  above  150°,  and  boiled 
with  water  without  decomposition.  Its  barium  salt  can  also  be 
boiled  with  caustic  potash  without  losing  sulphuric  acid.  He 
says,  "  I  propose  to  name  it  provisionally  benzoylsulphuric  acid, 
since  the  complexity  of  its  composition  necessitates  a  name 
which  gives  a  clue  to  its  constitution  without  indicating  it 
fully."2 

Fehling,  who  investigated  its  salts  more  closely,  observed  that 
when  heated  with  an  excess  of  caustic  potash  until  complete 
decomposition  has  taken  place,  it  yields  a  residue  containing 
both  sulphite  and  sulphate  of  potassium,  a  behaviour  which 
is  characteristic  of  the  salts  of  hyposulphuric  acid.  "  This  acid, 
therefore,  contains  hyposulphuric  and  not  sulphuric  acid,"  and  he 
therefore  called  it  benzoylhyposulphuric  acid.3 

It  was  then  investigated  with  great  care  by  Limpricht  and 
v.  Uslar,  who  recognised  it  as  a  sulphonic  acid.4 

It  is  also  formed  by  the  action  of  sulphuric  acid  on  benzonitril 5 
and  benzoyl  chloride,6  as  well  as  by  heating  the  latter  with  silver 
sulphate ; 7  and  by  treating  metadiazo-amidobenzoic  acid  with 
an  alcoholic  solution  of  sulphur  dioxide.8 

1  Journ.  Soc.  Chem.  Ind.  iv.  608  ;  Ber.  Deutsch.  Chem.  Ges.  xix.  Ref.  374. 

2  Ann.  Chem.  Pharm.  xii.  314. 

3  Ibid,  xxvii.  322. 

4  Ibid.  cii.  239  ;  cvi.  27. 

5  Buckton  and  Hofraann,  ibid.  c.  155. 

6  Oppenheim,  Ber.  Deutsch.  Chem.  Ges.  iii.  735. 

7  Carius  and  Kammerer,  Ann.  Chem.  Pharm.  cxxxi.  155  ;  Ador  and  Oppenheim, 
Ber.  Deutsch.  Chem.  Ges.  iii.  738  ;  Kammerer,  ibid.  iv.  219. 

8  Vollbrecht  and  Wiesinger,  ibid.  x.  715. 


270  AROMATIC  COMPOUNDS. 

In  order  to  prepare  metasulphobenzoic  acid,  the  vapour  of 
sulphur  trioxide  is  passed  over  benzoic  acid,  which  has  been 
previously  fused  and  powdered,  until  a  transparent  mass  is 
formed ;  or  two  parts  of  benzoic  acid  are  heated  with  one  part 
of  fuming  sulphuric  acid  for  some  time.  The  product  then 
contains  some  parasulphobenzoic  acid  in  addition  to  metasulpho- 
benzoic acid  and  free  sulphuric  acid.1  It  is  diluted  with  water, 
neutralized  with  barium  carbonate  and  filtered,  the  nitrate  being 
then  heated  and  treated  with  hydrochloric  acid.  The  acid  salt 
of  the  para-acid  crystallizes  out  first  on  cooling,  and  then  that  of 
the  meta-acid,  which  is  purified  by  recrystallization.  The  product 
of  the  reaction  may  also  be  saturated  with  milk  of  lime,  the 
filtrate  treated  with  potassium  carbonate,  and  the  potassium  salt 
which  is  thus  obtained,  recrystallized.2  Metasulphobenzoic  acid  is 
a  colourless,  crystalline  mass,  which  deliquesces  in  moist  air,  but 
solidifies  again  in  dry  air.  It  is  not  altered  by  boiling  nitric 
acid.  On  fusion  with  potash,  metahydroxybenzoic  acid  is  formed 
(Barth),  while  with  sodium  formate  it  yields  isophthalic  acid 
(v.  Meyer). 

The  Mctasnlphobenzoates.  Metasulphobenzoic  acid  is  a  power- 
ful dibasic  acid,  which  decomposes  even  barium  chloride  and 
barium  nitrate.  Its  normal  salts  are  usually  readily  soluble, 
while  the  acid  salts  dissolve  much  less  easily. 

Normal  potassium  metasulpholenzoate,  C7H4S05K2,  forms  de- 
liquescent crystals ;  the  acid  salt,  C7H5S05K,  crystallizes  in  long 
needles,  which  contain  two  and  half  or  five  molecules  of  water 
and  are  readily  soluble  in  water  and  alcohol.3 

Normal  barium  metasulpholenzoate,  C7H4SO5Ba  +  3H2O,  is 
very  soluble,  and  can  with  difficulty  be  obtained  in  well- 
developed  crystals ;  it  is  usually  deposited  in  crusts.  The  acid 
salt,  (C7H5Sb5)2Ba  +  3H2O,  dissolves  in  20  parts  of  cold  water, 
readily  in  hot  water  and  alcohol,  and  crystallizes  in  monoclinic 
prisms. 

Normal  lead  metasulpholenzoate,  C7H4S05Pb  +  2H2O,  is  much 
more  readily  soluble  in  hot  water  than  in  cold,  and  forms  fine, 
radiating  crystals,  resembling  those  of  wavellite. 

Silver  metasulpholenzoate,  C7H4SO5Ag2  4-  H2O,  crystallizes  in 
yellow  prisms  which  readily  dissolve. 

Normal  ethyl  metasulpholenzoate ,  C7H4SO5(C2H5)2.  is  prepared 
from  the  chloride  of  the  acid  and  absolute  alcohol,  and  forms  a 

1  Ann.  Che?n.  Pharm.  clxxviii.  275. 

2  Barth,  ibid,  cxlviii.  33.  3  Otto,  ibid,  cxxii.  155. 


MONOSULPHOBENZOIC  ACIDS.  271 

thick  liquid  which  has  a  faint  ethereal  odour,  and  decomposes  on 
heating.  It  is  soluble  in  water,  and  its  solution  decomposes 
when  heated  into  alcohol  and  the  acid. 

Acid  ethyl  metasulphobenzoate  or  Ethyl  metasulphobenzoic  acid, 
C7H5S06.C2H5.  The  ammonium  salt  of  this  acid,  C7H4SO5 
(NH4).C2H5,  is  obtained  by  passing  ammonia  into  an  alcoholic 
solution  of  the  normal  ether  or  by  the  action  of  alcoholic 
ammonia  on  the  chloride.  It  crystallizes  in  large,  four-sided, 
transparent  tablets.  If  the  ammonia  be  precipitated  with 
platinum  chloride,  and  the  excess  of  platinum  removed  by 
sulphuretted  hydrogen,  a  solution  of  the  free  acid  is  obtained ; 
its  salts  crystallize  well  and  are  readily  soluble.  Its  constitution 
is  probably  represented  by  the  former  of  the  two  following 
formulas  : 

/S03H  /S03.C2H5 

CTJ    /  C\   TT   / 

6M4\  U«*14\ 

\C02.C2H5  \C02H 

Metasulphdbenzoyl  chloride,  C7H4S03C12,  is  obtained  by  heating 
the  dry  acid  with  phosphorus  pentachloride;  the  phosphorus 
oxychloride  is  then  distilled  off  and  the  residue  washed  with 
water.  It  is  a  thick,  oily  liquid,  which  has  a  faint  but  unpleasant 
odour,  and  decomposes  on  distillation  into  sulphur  dioxide  and 
metachlorobenzoyl  chloride.  The  latter  is  also  formed  when  the 
compound  is  heated  to  140° — 150°  with  phosphorus  pentachloride. 
When  it  is  allowed  to  stand  for  some  time  in  contact  with  water 
or  when  the  acid  is  acted  upon  by  one  molecule  of  phosphorus 
pentachloride,  the  monochloride  is  formed  : 

Cj  f\      /~\TJ~  O  /~\    /^11 

xDL/2.V>>JLjL  ,/k5VJ9v^l 

C6H4x  or     C6H4v 

\COC1  \CO.OH 

This  separates  from  ether  in  warty  masses,  and  is  decomposed 
by  boiling  water,  &c.,  with  formation  of  metasulphobenzoic 
acid. 

Metasulpholcnzamide,  C7H4SO3(NH2)2,  is  formed  by  the  action 
of  concentrated  aqueous  ammonia  on  the  chloride.  It  is  almost 
insoluble  in  cold  water  and  crystallizes  from  hot  water  or  ordinary 
alcohol  in  needles  containing  a  molecule  of  water,  while  it 
separates  from  absolute  alcohol  in  small,  vitreous,  anhydrous 
crystals. 


272  AROMATIC  COMPOUNDS. 

When  it  is  heated  with  phosphorus  pentachloride  the  following 
reaction  takes  place  : 

/S02NH2  XSO9.NH2 

C6H/  +  PCL  =  C6H4<  +  POOL  +  HC1. 

\CO.NH2  \CC1=NH 

The  imido-chloride  which  is  thus  formed  has  not  been  obtained 
pure  ;  *  it  decomposes  on  distillation  with  formation  of  meta- 
chlorobenzonitril,  while  ammonia  or  water  converts  it  into 
sulpliamidobenzonitril,  CN.C6H4.SO2.NH2,  which  separates  from 
alcohol  in  crystals,  melting  at  152°  —  153°. 

Metasulphamidobenzoic  acid,  C7H7NS04,  is  formed  when  the 
nitril  or  amide  is  heated  with  caustic  potash  solution  : 

/S02.NH2  /S02.NH2 

C6H4<  +  KOH  =  C6H4<  +  NH3. 

\CO.NH2  \CO.OK 

It  is  slightly  soluble  in  cold  water,  and  crystallizes  from  a 
hot  solution  in  scales  resembling  those  of  potassium  chlorate, 
and  melting  above  200°.  It  is  a  monobasic  acid,  and  forms 
crystallizable  salts. 

Ethyl  metasulphamidobenzoate,  C7H6(C2H5)NSO4,  is  obtained 
by  heating  the  silver  salt  with  ethyl  iodide,  or  by  passing  hydro- 
chloric acid  into  an  alcoholic  solution  of  the  acid.  It  is  also 
formed  when  ammonia  is  passed  into  a  solution  of  sulphobenzoyl 
chloride  in  a  mixture  of  alcohol  and  ether.  It  crystallizes  from 
alcohol  in  monoclinic  prisms.2 


Metathiohydrobenzoic   acid,   C6H4<  ,  is  prepared  by  the 


action  of  tin  and  hydrochloric  acid  on  metasulphobenzoyl  chloride. 
It  is  tolerably  soluble  in  water,  more  readily  in  alcohol,  and 
sublimes,  when  heated  in  a  current  of  carbon  dioxide,  in  flat 
needles,  melting  at  146°  —  147°.  It  oxidizes  when  exposed  to  the 
air  in  a  moist  state,  or  more  rapidly  when  acted  upon  by  bromine 
water,  to  metadithiobenzoic  acid,  S2(C6H4.CO2H)2,  which  is  scarcely 
soluble  in  water,  and  only  slightly  in  alcohol,  crystallizing  from 
the  latter  in  short  needles  which  melt  at  24G°—  -2470.3 

1  Huth  and  Wallach,  Ber.  Deutsch.  Chem.  Ges.  ix.  427. 

2  Hart,  Amer.  Chem.  Journ.  i.  342. 

3  Frehrichs,  Ber.  Deutsch.  Chem.  Ges.  vii.  792. 


PARASULPHOBENZOIC  ACID.  273 

2155  Parasulphobenzoic  acid  is  obtained  by  the  oxidation  of 
paratoluenesulphonic  acid ;  it  is  not  necessary  to  employ  pure 
material  for  its  preparation,  and  the  mixture  of  the  three  isomeric 
acids  which  is  obtained  by  dissolving  toluene  in  sulphuric  acid 
may  be  conveniently  made  use  of.  The  para-compound  is  the 
chief  constituent  of  the  mixture,  and,  together  with  the  meta- 
acid,  is  readily  oxidized,  while  the  ortho-acid  remains  unaltered 
(Remsen). 

One  hundred  grammes  of  toluene  are  dissolved  in  the  smallest 
possible  quantity  of  fuming  sulphuric  acid,  the  solution  made  up 
to  five  litres  with  water,  and  heated  until  it  becomes  colourless. 
Hydrochloric  acid  and  barium  chloride  are  then  added  to  the 
filtrate  and  the  precipitated  acid  barium  salt  purified  by  re- 
crystallization  ;  200  grammes  of  it  are  obtained  in  this  way.1 

It  is  also  formed  by  the  action  of  alcoholic  sulphurous  acid  on 
paradiazobenzoic  acid  (Vollbrecht  and  Wiesinger). 

Parasulphobenzoic  acid  is  readily  soluble  in  water,  and 
crystallizes  in  needles,  which  are  not  deliquescent  and  melt 
with  decomposition  at  about  200°.  On  fusion  with  caustic 
potash,  parahydroxybenzoic  acid  is  formed,  while  with  potas- 
sium formate  it  yields  terephthalic  acid. 

The  potassium  salt  forms  transparent  needles  which  easily 
dissolve. 

Normal  "barium  parasulpfiolenzoate,  C7H4S05Ba-f-2H2O, 
crystallizes  in  small,  tolerably  soluble  needles.  The  acid  salt, 
(C7H5SO5)2Ba  +  3H2O,  is  slightly  soluble  in  hot  water,  and 
forms  long,  flat,  lustrous  needles. 

,S02.NH2 

Parasulphamidobenzoic  acid,  CflH-\  ,    is   formed  by 

\CO.OH 

the  oxidation  of  paratoluenesulphamide  with  chromic  acid 
solution.  It  is  almost  insoluble  in  cold,  slightly  soluble  in  hot 
water,  and  readily  in  alcohol,  crystallizing  in  long,  flat,  lustrous 
prisms. 

1  Hart,  loc.  cit. 


274  AROMATIC  COMPOUNDS. 


/SO,H 

DISULPHOBENZOIC   ACIDS,  C6H/-CO2H. 

\SO3H 

2156  a-Disulphobenzoic  acid  (2  :  4)  is  obtained  by  the  oxida- 
tion of  a-toluenedisulphonic  acid.1  It  is  readily  soluble  in 
water,  insoluble  in  alcohol,  and  is  deposited  from  solution  in 
concentrated  hydrochloric  acid  in  large  crystals,  melting  above 
285°.  On  heating  to  250°  with  caustic  potash,  the  asymmetric 
dihydroxybenzoic  acid  melting  at  204°  is  formed  ;  at  a  higher 
temperature  resorcinol  is  obtained. 

ft-Disulphobenzoic  acid  (3  :  5)  is  formed  when  benzoic  acid  is 
heated  to  250°  Avith  fuming  sulphuric  acid  and  phosphorus 
pentoxide.  It  is  a  white,  hygroscopic,  crystalline  mass,  which 
on  fusion  with  potash  yields  the  asymmetric  dihydroxybenzoic 
acid,  which  melts  at  232°  —  233°,  while  resorcinol  is  formed  when 
it  is  heated  to  350°  with  caustic  soda.2 

Both  compounds  are  strong  tribasic  acids. 

/SO3H 
CHLOROSULPHOBENZOIC  ACIDS,  CrH,Cl< 

\C02H 

2157  Four  of  these  compounds  are  known.  The  first  is  obtained 
by  the  oxidation  of  orthochlorotoluenesulphuric  acid,3  the  second 
by  the  action  of  sulphur  trioxide  on  metachlorobenzoic  acid,4 
and  the  last  two,  one  of  which  only  has  been  examined,  from 
parachlorobenzoic  acid.5 


BROMOSULPHOBENZOIC  ACIDS,  CfiH,Br< 

\C02H 

One  of  these  derivatives  has  been  prepared  by  the  oxidation 
of  orthobromotoluene,6  a  second  from  metabromobenzoic  acid 
and  sulphur  trioxide,7  and  two  others  by  the  oxidation  of  the 
isomeric  parabromotoluenesulphonic  acids,8  one  of  them  having 
been  also  obtained  from  parabromobenzoic  acid.9 

1  Blomstrand,  Bcr.  Deutsch.  Chem.  Gcs.  v.  1084  ;  Fahlber^,  Amcr.  Chem. 
Journ.  ii.  181.  2  Earth  and  Senhofer,  Ann.  Chem.  Pharm.  clix.  271. 

3  Hiibner  and  Majert,  Ber.  Deutsch.  Chem.  Ges.  vi.  792. 

4  Otto,  Ann.  Chem.  Pharm.  cxxiii.  216. 

5  Bbttinger  and  Coll  en,  ibid.  cxci.  29. 

6  Hiibner  and  Retschy,  ibid,  clxix.  45. 

7  Hiibner  and  Upmann,  Zeitsch.  Chem.  1870,  295  ;  Hiibner  and  Lennep,  ibid. 
1871,  67.  8  Hiibner  and  Post,  Ann.  Chem.  Pharm.  clxix.  6. 

9  Bb'ttinger,  ibid.  cxci.  13. 


NITROSULPHOBENZOIC  ACIDS.  275 


/S03H. 
NITROSULPHOBENZOIC   ACIDS,  C6H3(N02) 


2158  Mulder,  as  early  as  the  year  1840,  prepared  a  nitro- 
sulpho'benzoic  acid  by  the  action  of  fuming  sulphuric  acid  on 
metanitrobenzoic  acid,  but  did  not  investigate  it.  Limpricht 
and  v.  Uslar  then  obtained  one  by  the  nitration  of  meta- 
sulphobenzoic  acid.1  Remsen  prepared  another  from  parasulph- 
amidobenzoic  acid  2  in  the  same  way,  and  Hart  obtained  the 
same  compound  by  nitrating  parasulphobenzoic  acid.  He  also 
prepared  another^  isomeride  from  orthosulphobenzoic  acid  and 
two  additional  ones  by  the  oxidation  of  the  corresponding  nitro- 
toluenesulphonic  acids. 


AMIDOSULPHOBENZOIC  ACIDS. 

Two  of  these  compounds  have  been  obtained  by  the  action  of 
sulphuric  acid  on  metamidobenzoic  acid.3  One  of  these  and 
three  others  are  formed  when  the  corresponding  nitrosulpho- 
benzoic  acids  are  reduced.4 


XPO(OH)2 
BENZOPHOSPHINIC    ACID,  C6H4( 

XCO.DH 

2159  This  body  may  be  readily  obtained  by  dissolving  10 
grams,  of  paratolylphosphinic  acid  in  a  litre  of  water,  adding  an 
excess  of  caustic  potash,  heating  to  50°,  and  then  running  in  a 
solution  of  18'4  grams,  of  potassium  permanganate.  The  latter 
is  completely  reduced  after  about  a  week,  and  the  solution  is 
then  filtered,  acidified  with  acetic  acid  and  evaporated.  The 
potassium  acetate  is  extracted  from  the  residue  by  alcohol,  and 
the  residual  acid  potassium  benzophosphinite  dissolved  in  hot, 
concentrated  hydrochloric  acid,  the  benzophosphinic  acid  being 

1  Bbttinger,  Ann.  Chem.  Pharm.  cvi.  27. 

2  Ibid,  clxxviii.  288  ;  Hart,  Amer.  Chem.  Journ.  i.  342. 

3  Griess,  Journ.  Prakt.  Chem.  [2]  v.  244. 

4  Limpricht  and  v.  Uslar  ;  Hart, 


276  AROMATIC  COMPOUNDS. 

deposited  from  this  solution  on  cooling  in  transparent,  lustrous, 
striated  tablets,  which  are  readily  soluble  in  water,  and  crystal- 
lize from  it  in  matted  needles  with  a  satin  lustre. 

It  melts  above  300°,  and  decomposes  when  more  strongly 
heated,  one  portion  becoming  carbonized  while  the  remainder 
decomposes  into  benzoic  and  metaphosphoric  acids.  It  is  not 
attacked  by  bromine  and  water  at  130°,  while  tolylphosphinic 
acid  is  decomposed  by  these  at  the  ordinary  temperature  into 
phosphoric  acid  and  bromotoluene. 

It  is  a  tribasic  acid,  but  readily  forms  acid  salts. 

Acid  potassium  benzophosphinate,  C6H4(P03H2)CO2K-f  H0O, 
crystallizes  in  fine  needles,  which  are  readily  soluble  in  water, 
slightly  in  alcohol.  When  hydrochloric  acid  is  added  to  its 
solution,  the  double  salt,  C6H4(PO3H2)C02K+C6H4(PO3H2)C02H, 
separates  out ;  it  crystallizes  from  hot  water  in  small  prisms.  It 
may  also  be  obtained  as  a  precipitate  resembling  cream  of  tartar, 
by  adding  the  free  acid  to  a  tolerably  concentrated  solution  of  a 
potassium  salt. 

Silver  benzophosphinate,  C6H4(P03Ag2)CO2Ag,  is  obtained  as 
an  amorphous  precipitate  by  adding  silver  nitrate  to  a 
solution  of  the  acid  neutralized  with  ammonia.  Oil  heating 
with  methyl  iodide,  the  methyl  ether  is  formed  as  a  thick  liquid, 
which  decomposes  on  boiling. 

Benzophosphine  chloride,  C6H4(POC12)COC1,  is  formed  by  the 
action  of  phosphorus  chloride  on  the  acid ;  it  is  a  crystalline 
mass,  melts  at  83°,  boils  at  315°,  and  is  attacked  by  cold  water, 
but  is  readily  decomposed  by  boiling  water.1 

Trimethylphosphobenzobetame,  C6H4(CO.O)P(CH3)3  +  3H20- 
The  chloride  of  this  compound  is  formed  by  the  oxidation  of 
trimethylparatolylphosphonium  chloride  with  potassium  per- 
manganate : 

/CH3  /CO.OH 

C6H4<  +30  =  C6H4<;  +H20. 

.  XP(CH3)3C1  XP(CH3)3C1 

It  crystallizes  in  short,  lustrous  prisms,  which  are  readily 
soluble  in  water,  less  so  in  alcohol.  The  base,  which  is  liberated 
by  alkalis,  crystallizes  from  hot  alcohol  in  rhombohedra,  which 
deliquesce  in  the  air.  When  the  chloride  is  heated  with  an 
excess  of  caustic  potash  solution  it  decomposes  with  formation 
of  benzoic  acid  and  trimethylphosphine  oxide. 

1  Michaelis  and  Panek,  Bcr.  Dcutsch.  Chem.  Gcs.  xiv.  405. 


BENZAESENIC  ACIDS.  277 

Dimethylphospliinc-oxide  benzoic  add,  C6H4.PO(CH3)2.C02H,  is 
formed  by  the  oxidation  of  dimethyltolylphosphine  oxide,  and 
crystallizes  in  prisms  which  have  a  feebly  acid  taste,  melt  at 
243°,  sublime  almost  without  decomposition,  and  are  not  easily 
attacked  by  caustic  potash  solution.1 


BENZARSENIC   ACIDS. 

2160  Benzarsenic  acid,  C6H4(As03H2)C02H,  is  obtained  by 
oxidizing  paratolylarsenic  acid  in  alkaline  solution.  It  is  only 
slightly  soluble  in  water,  and  crystallizes  in  large,  transparent 
tablets  or  nacreous  plates.  On  heating  the  anhydride,  arseno- 
benzoic  acid,  C6H4(AsO2)C02H,  is  formed  ;  this  compound,  which 
corresponds  to  paranitrobenzoic  acid,  is  a  yellowish  powder, 
soluble  in  hot  alcohol. 

Acid  potassium  benzar  senate,  C6H4(As03H2)C02K  +  C6H4 
(As03H2)CO2H,  crystallizes  from  hot  water  in  transparent, 
triclinic  tablets. 


Acid    calcium    benzar  senate,    C6H 

C 


forms  nacreous  plates,  slightly  soluble  in  water. 

Silver  benzarsenate,  C6H4(AsO3Ag2)CO2Ag,  is  an  amorphous 
precipitate,  which  yields  the  crystalline  methyl  ether  on  heating 
with  methyl  iodide. 

Benzarsene  chloride,  C6H4(AsCl.2)C02H,  is  obtained  by  the 
action  of  phosphorus  trichloride  on  the  acid  : 

C6H4(As03H2)C02H  +  2PC13  = 

C6H4(AsCl2)COCl  +  POC13  +  P(OH)3. 

The  product  of  the  reaction  is  carefully  treated  with  water, 
and  yields  the  chloride,  crystallizing  in  needles,  which  melt  at 
157° — 158°,  and  are  decomposed  by  boiling  water. 

Benzarsene  iodide,  C6H4(AsI2)C02H,  is  formed  by  the  action  of 
hydriodic  acid  and  phosphorus  on  the  acid,  and  crystallizes  from 
chloroform  in  yellow  needles,  melting  at  153°. 

Benzarsenious  acid,  C6H4As(OH)2CO2H,  is  prepared  by  dis- 
solving the  iodide  in  carbonate  of  soda  and  precipitating  with 
hydrochloric  acid ;  it  is  thrown  down  in  crystals,  and  crystallizes 

1  Michaelis  and  Czimatis,  Bcr.  Dcutsch.  Chem.  Ges.  xv.  2018. 
249 


278  AROMATIC  COMPOUNDS. 

from  hot  water  in  fine  needles,  which  are  converted  into  the 
anhydride,  C6H4(AsO)CO2H,  at  160°. 

Calcium  benzarsenite,  (C6H4(AsO2H2)C02)2Ca,  crystallizes  in 
nacreous  plates,  which  lose  a  molecule  of  water  on  heating. 
Silver  nitrate  added  to  its  solution  produces  a  white  precipitate 
of  silver  benzarsenite,  C6H4(AsO)CO2Ag. 

Dibenzarsenic  acid,  (C6H4.C02H)2AsO.OH,  is  formed  by  the 
oxidation  of  paraditolylarsenic  acid  with  potassium  permanganate 
and  forms  fine,  lustrous  plates,  which  are  scarcely  soluble  in  water, 
and  only  slightly  in  alcohol  and  hydrochloric  acid.  Its  salts  do 
not  crystallize  well. 

Dibenzarsene  iodide,  (C6H4.CO2H)2AsI,  is  obtained  by  heating 
the  acid  with  hydriodic  acid  and  amorphous  phosphorus.  It 
is  a  crystalline  mass  which  dissolves  in  alcohol  and  ether,  and 
melts  above  280°. 

Dibenzarsenious  acid,  (C6H4.C02H)2AsOH,  is  prepared  by  de- 
composing the  iodide  with  sodium  carbonate  ;  on  the  addition  of 
hydrochloric  acid,  it  is  obtained  as  a  crystalline  precipitate, 
which  is  slightly  soluble  in  water,  more  readily  in  alcohol. 

Calcium  dibenzarsenite,  HOAs(C6H4.C02)2Ca  +  2H2O,  is  pre- 
cipitated by  alcohol  from  its  aqueous  solution  as  a  white 
powder. 

Tribenzarsenic  acid,  (HO)2As(C6H4.C02H)3,  is  formed  when 
tritolylarsine  is  oxidized ;  it  is  tolerably  soluble  in  water  and 
separates  from  alcohol  in  crusts,  from  ether  in  granular 
crystals. 

Potassium  tribenzar senate,  AsO(C6H4.C02K)3,  separates  from 
alcohol  in  crystalline  crusts,  which  are  readily  soluble  in 
water. 

Tribenzarsenious  acid,  or  Arsenetribenzoic  acid,  As(C6H4.CO2H)3, 
is  obtained  by  the  reduction  of  tribenzarsenic  acid  with  hydriodic 
acid  and  phosphorus  ;  it  crystallizes  from  ether,  in  small,  colourless 
needles. 

Sodium  arsenetribenzoate,As(C6H.4:.CO2^8i)s  +  2H20,  crystallizes 
from  hot  water  in  short,  fine  needles.  The  silver  salt  is  a 
yellowish  precipitate.1 

1  La  Coste,  Ann.  Chcm.  Pharm.  ccviii.  1. 


HYDROXYBENZYL  GROUP.  279 


HYDROXYBENZYL  GROUP. 

/OH 
HYDROXYBENZYL  ALCOHOLS,  C6H4< 


2161  Orthohydroxybenzyl  alcohol.  Piria,  in  1845,  found  that 
salicin,  which  is  contained  in  willow  bark,  is  split  up  by 
the  action  of  dilute  acids  or  of  emulsin  (p.  130)  into 

grape  sugar  and  a  new  compound  which  he  therefore  named 
.1 

C13H1807  +  H20  =  C6H1206  +  C7H802. 

This  substance,  which  was  subsequently  also  called  salicyl 
alcohol,  because  it  was  found  to  stand  to  salicylic  acid  in  the 
same  relation  as  benzyl  alcohol  to  benzoic  acid,  was  obtained  by 
Beilstein  and  Reineke  by  the  action  of  sodium  amalgam  and 
water  on  salicyl  aldehyde,2  and  Greene  found  that  it  is  also 
formed  when  phenol  is  heated  with  methylene  chloride  and 
caustic  soda  solution  : 3 

/OH 
C6H5.ONa  +  CH2C12  +  NaOH=C6H4<  +  2NaCl. 


The  decomposition  of  salicin  by  dilute  acids  cannot  be 
employed  for  its  preparation,  since  a  portion  of  the  alcohol  is 
converted  into  saliretin  (p.  280),  and  the  following  method, 
devised  by  Piria,  is  therefore  made  use  of.  Fifty  parts  of  salicin 
are  brought  into  200  parts  of  water,  and  3  parts  of  emulsin  added, 
this  substance  being  obtained  by  macerating  pressed  almonds  with 
3  parts  of  water  for  two  hours,  and  precipitating  the  solution  with 
alcohol.  After  twelve  hours  the  greater  portion  of  the  saligenin 
has  crystallized  out,  and  the  remainder  is  extracted  from  the 

1  Ann.  Chem.  Pharm.  Ivi.  37. 

2  Beilstein  and  Reineke,  ibid,  cxxviii.  179. 

3  Amer.  Chem.  Journ.  ii.  19. 


280  AROMATIC  COMPOUNDS. 

solution  with  ether.      The  crude  product  is  then  re-crystallized 
from  hot  benzene.1 

Orthohydroxybenzyl  alcohol  dissolves  in  15  parts  of  water  at 
22°,  and  in  almost  all  proportions  in  boiling  water,  readily  in 
alcohol  and  ether.  It  crystallizes  in  small  rhombohedra,  or  tablets, 
which  melt  at  82°  and  sublime  at  100°.  It  forms  a  bluish  red 
solution  in  sulphuric  acid,  and  its  aqueous  solution  is  coloured 
deep  blue  by  ferric  chloride. 

Saliretin,  C14HUO3  =  C6H4(OH)CH2O.C6H4,CH2OH.  Bracon- 
not  found  that  concentrated  sulphuric  acid  converts  salicin  into 
a  resinous  substance,  and  Piria,  who  observed  that  dilute  acids 
have  the  same  effect,  gave  the  product  its  name,  which  is 
intended  to  suggest  both  its  nature  and  source.2 

Saliretin  is  formed  from  salicin  by  elimination  of  the  elements 
of  water ;  in  order  to  prepare  it,  salicin  is  heated  to  80°  with 
10  parts  of  fuming  hydrochloric  acid,  the  product  precipitated  by 
water,  dissolved  in  dilute  alcohol  and  again  precipitated  by  a 
solution  of  salt.3 

It  is  a  yellowish  powder,  which  dissolves  in  alkalis  and  does 
not  yield  either  salicylaldehyde  or  salicylic  acid  on  oxidation. 
Concentrated  nitric  acid  converts  it  into  picric  acid. 

The  saliretin  obtained  by  the  action  of  concentrated  sulphuric 
acid  has  the  formula  C28H2605,4  while  a  compound,  C56H5009,  is 
formed  by  heating  saligenin  with  acetic  anhydride  (Beilstein  and 
Seelheim). 

Salireton,  C14H1203,  is  formed  in  small  quantity,  together  with 
other  resinous  products,  when  saligenin  is  heated  with  glycerol. 
It  crystallizes  from  hot  water  in  plates  or  needles,  which  melt  at 
121 '5°,  are  coloured  red  by  strong  sulphuric  acid,  and  are  not 
affected  by  ferric  chloride.5 

Orthohydroxybenzyl  methyl  ether,  or  Orthomethoxybenzyl  alcohol, 
C6H4(OCH3)CH2OH,  is  formed  when  saligenin  is  heated  with 
methyl  iodide,  caustic  potash  and  wood  spirit ;  it  is  a  liquid, 
which  boils  at  247'5°  and  solidifies  in  a  mixture  of  ether  and  solid 
carbonic  acid  to  a  glassy  mass.6 

Orthohydroxylenzyl    ethyl   ether,    C6H4(OC2H5)CH2.OH,   is 
pleasant  smelling  liquid,  which  boils  at  265°  and  solidifies  at  Oc 

1  Beilstein  and  Seelheim,  Amer.  Chem.  Journ.  cxvii.  84. 

2  Ann.  Chem.  Pharm.  xxx.  179. 

3  Kraut,  ibid.  clvi.  124. 

*  Gerhardt,  Ann.  Chim.  Phys.  [3]  vii.  215. 

6  Giacosa,  Journ.  Prakt.  Chem.  [2]  xxi.  221. 

6  Cannizzaro  and  Korner,  Ber.  Deutsch.  Chem   Ges.  v.  436. 


SALICIN.  281 


to  a  crystalline  mass.  It  gives  no  colouration  with  ferric  chloride, 
and  is  oxidized  by  dilute  nitric  acid  to  ethoxybenzoic  acid  or  ethyl 
salicylic  acid,  C^OC^CO.OH.1 

Caffeol,  C8H10O2.  When  coffee  beans  are  roasted,  the  follow- 
ing substances  are  given  off  from  100  parts:  0*05  of  caffeol, 
0'18  of  caffeine,  0'48  of  fatty  acids,  chiefly  palmitic  and  acetic, 
carbon  dioxide  and  small  quantities  of  pyrrol,  methylamine  and 
quinol,  derived  probably  from  the  quinic  acid  which  is  contained 
in  the  beans. 

Caffeol  is  a  liquid  which  boils  at  195° — 197°,  and  possesses 
the  fine  aroma  of  coffee  in  a  very  marked  degree.  Its  alcoholic 
solution  gives  with  ferric  chloride  a  red  colouration  which  is  not 
destroyed  by  sodium  carbonate.  It  only  dissolves  with  difficulty 
in  concentrated  caustic  potash  solution,  and  on  fusion  with 
caustic  potash  yields  salicylic  acid ;  it  is  probably  therefore  a  methyl 
ether  of  saligenin,  and  has  the  constitution  C6H4(OH)CH2.OCH3.2 
The  fact  that  it  gives  a  red  colouration  with  ferric  chloride 
which  shows  it  to  be  a  phenol,  is  in  accordance  with  this  sup- 
position. Rotsch  has  also  found  that  hydroxybenzyl  methyl 
ether,  already  mentioned,  which  is  isomeric  with  caffeol,  smells 
strongly  of  burnt  coffee,  but  loses  the  smell  completely  on 
purification.  This  behaviour  may  be  explained  by  the  formation 
of  small  quantities  of  caffeol  as  a  by-product,  to  which  the  crude 
product  owes  its  smell. 

2162  Salicin,  or  Orthohydroxylenzyl  glucoside,  C6H4(CH2.OH) 
OC6H11O5.  After  several  chemists  had  unsuccessfully  endeavoured 
to  obtain  the  bitter  principle  of  willow-bark,  which  was  recom- 
mended in  cases  of  intermittent  fever  as  a  substitute  for  quinine, 
in  the  pure  state,  Leroux  succeeded  in  purifying  it  to  such  an 
extent  that  it  could  be  readily  crystallized.3  It  was  at  first 
thought  to  be  an  alkaloid,  although  this  was  afterwards  shown 
not  to  be  the  case,  and  the  difficulty  experienced  in  obtaining 
compounds  of  it  with  other  substances  prevented  chemists 
from  examining  it  more  closely  until  Piria  subjected  it  to  a 
careful  investigation,  which  resulted  in  a  complete  explanation 
of  its  nature.4 

It  occurs  in  the  bark,  leaves,  and  female  flowers  of  many 
trees  which  do  not  all  belong  to  the  willow  tribe,  and  to  the 
extent  of  4  per  cent,  in  Salix  helix,  pentandra,  and  prcecox\  it 

1  Rotsch,  Monarch.  Chem.  i.  621.  2  Bernheimer,  ibid.  i.  456. 

8  ^TtTi.  Chim.  Phys.  xliii.  440. 
.  4  Ann.  Cham.  Pharm.  xxx.  151  and  189  ;  Ivi.  49 ;  Liebig,  ibid.  xxx.  185. 


AROMATIC  COMPOUNDS. 


has  also  been  found  in  the  bark  and  leaves  of  the  poplar,1  in 
the  flower  buds  of  Spirwa  Ulmaria  (p.  286)  and  in  castoreum 2 
(Wohler). 

In  order  to  prepare  it,  3  parts  of  willow-bark  are  extracted 
three  times  with  boiling  water,  the  extract  evaporated  down 
to  9  parts,  digested  for  twenty-four  hours  with  1  part  of  litharge, 
filtered  and  evaporated  to  a  syrup.  The  salicin  separates  out 
and  is  purified  by  re-crystallization.3  It  forms  needles,  plates,  or 
rhombic  prisms,  which  dissolve  in  30  parts  of  water  at  the 
ordinary  temperature,  and  freely  in  hot  water  and  alcohol,  but 
are  insoluble  in  ether ;  it  has  a  very  bitter  taste,  and  forms  a 
purple-red  solution  in  sulphuric  acid.  Dilute  nitric  acid  oxidizes 
it  to  helicin,  C6H4(CHO)OC6HUO5  (p.  288),  which  may  be  re- 
converted into  salicin  by  sodium  amalgam  and  water.  As 
helicin  can  be  artificially  prepared  by  the  action  of  acetochloro- 
hydrose  on  salicyl  aldehyde,  it  is  also  possible,  as  Michael  has 
shown,  to  prepare  salicin  artificially ;  this  is  the  first  instance  of 
the  synthesis  of  a  glucoside  occurring  in  nature.4 

Salicin  melts  at  201°,  and  solidifies  on  cooling  to  a  crystalline 
mass ;  when  it  is  heated,  however,  for  some  time  to  230° — 
240°,  it  partially  decomposes  into  saliretin  and  glucosane5 
(Part  II.  p.  540).  Its  aqueous  solution  rotates  the  plane  of 
polarization  to  the  left.6  When  taken  internally  a  portion  of  it 
appears  in  the  urine  as  saligenin,  salicylaldehyde  and  salicylic 
acid,  the  remainder  being  excreted  unchanged ; 7  its  occurrence 
in  castoreum  is  thus  explained.  It  is  used  in  medicine  in  cases 
of  intermittent  fever,  acute  rheumatism,  &c.,  and  is  also  employed 
for  adulterating  quinine. 

Populin,  or  Benzoylsalicin,  C13H17(C6H5.CO)07  -f  2H20,  was 
discovered  by  Braconnot  in  the  bark  and  leaves  of  the  aspen 
poplar,  Popidus  tremula*  and  carefully  investigated  by  Piria.9 
Piccard  also  observed  it,  along  with  salicin  and  other  substances, 
in  the  buds  of  Populus  pyramidalis,  nigra  et  balsamifera,10  and 
SchifF  obtained  it  artificially  by  fusing  salicin  with  benzoic 
anhydride.11 


1  Braconnot,  Ann.  Chim.  Phys.  xliv.  296  ;  Tischhausen,  Ann.  Chem.  Pharm. 
vii.  280.  2  Ibid.  Ixvii.  360. 

3  Duflos,  ibid.  viii.  200.  4  Amer.  Chem.  Journ.  v.  171. 

5  Schiff,  Ber.  Deutsch.  Chem.  Gcs.  xiv.  304. 

6  Hesse,  Ann.  Chem.  Pharm.  clxxvi.  116. 

7  Laveran  and  Millon,  ibid.  lii.  435  ;  Ranke,  Jahresb.  Chem.  1852,  711. 

8  Ann.  Chim.  Phys.  xliv.  296. 

9  Ann.  Chem.  Pharm.  Ixxxi.  245  ;  xcvi.  375. 

10  Ber.  Deutsch.  Chem.  Ges.  vi.  890.  n  Ann.  Chem.  Pharm.  cliv.  5. 


BENZOYLSALICIN.  283 


It  crystallizes  in  extremely  thin  needles,  which  dissolve  in 
2,420  parts  of  water  at  15°  and  in  42  parts  at  100°;  it  loses  its 
water  of  crystallization  at  100°  and  melts  at  180°.  Its  taste 
resembles  that  of  liquorice  ;  it  is  coloured  amaranthine  red  by 
sulphuric  acid.  Boiling  baryta  water  decomposes  it  into  saliciu 
and  benzoic  acid ;  emulsin  has  no  action  upon  it,  but  on  boiling 
with  a  dilute  acid  it  yields  saliretin,  benzoic  acid  and  dextrose,1 
while  salicin,  benzamide,  and  ethyl  benzoate  are  obtained  by 
heating  it  with  alcoholic  ammonia.  Nitric  acid  oxidizes  it  to 
benzoyl-helicin,  which  is  the  corresponding  aldehyde.  It  has, 
therefore,  the  following  constitution : 

/CH2.OH 

c6n  / 

\OC6H10(CO.C6H5)05 

2163  Metahydroxybenzyl  alcohol  is  obtained  by  the  action  of 
sodium  amalgam  on  an  aqueous  solution  of  metahydroxybenzoic 
acid  which  is  kept  acid  by  the  repeated  addition  of  small 
quantities  of  hydrochloric  acid.  It  is  readily  soluble  in  alcohol 
and  hot  water,  crystallizes  in  tough  needles,  melts  at  63°,  and 
boils  with  partial  decomposition  at  about  300° ;  its  aqueous 
solution  is  coloured  violet-blue  by  ferric  chloride.  Hydrochloric 
acid  converts  it  into  a  viscid  resin,  and  on  fusion  with  caustic 
potash  it  is  oxidized  to  metahydroxybenzoic  acid. 

Metahydroxybenzyl  acetate,  C6H4(OH)CH2.O.C2H3O,  is  formed 
by  the  action  of  a  mixture  of  acetic  and  sulphuric  acids 
on  the  alcohol,  and  forms  crystals  which  melt  at  55°  and 
only  very  slightly  soluble  in  water ;  the  solution  is 
coloured  violet-blue  by  ferric  chloride.  It  boils  with  decom- 
position at  295°— 302°. 

Metahydroxybenzyl  diacetate,  or  Meta-acetobenzyl  acetate,  C6H4 
(OC2H3O)CH2.OC2H3O,  is  formed  by  heating  the  alcohol  to 
160°  with  acetic  anhydride,  and  is  a  liquid  which  boils  at  290°, 
and  does  not  give  a  colouration  with  ferric  chloride.2 

Pardhydroxybenzyl  alcohol  is  obtained  by  the  action  of  sodium 
amalgam  on  a  solution  of  parabenzaldehyde  in  dilute  alcohol 
acidified  with  sulphuric  acid.  It  is  readily  soluble  in  water, 
alcohol  and  ether,  and  crystallizes  in  needles,  melting  at  110°.  It 
forms  a  splendid  reddish  violet  solution  in  concentrated  sulphuric 
acid.3 

1  Schmidt,  Ann.  Chem.  Pharm.   xix.  92. 

2  Velden,  Journ.  Pralet  Chem.  [2]  xv.  165. 

3  Biedermann,  Ber.  Deutsch.   Chem.  Ges.  xix.  2373. 


284  AROMATIC  COMPOUNDS. 

Parahydroxyl>enzyl  methyl  ether,  or  Anise  alcohol,  C6H4(OCH3) 
CH2.OH,  is  formed  by  the  action  of  alcoholic  potash  on  anis- 
aldehyde  (paramethoxybenzaldehyde).1  It  is  also  formed  when 
parahydroxybenzyl  alcohol  is  heated  with  methyl  iodide  and 
caustic  potash,  and  crystallizes  in  hard,  lustrous  needles,  which 
have  a  faint  spirituous  odour  and  a  burning  taste  ;  it  melts  at 
25°,  and  boils  at  258'8°.2 

Paramethoxylenzyl  chloride,  C6H4(OCH3)CH2C1,  is  prepared  by 
saturating  the  alcohol  with  hydrochloric  acid  ;  it  is  a  liquid  with 
a  fruity  odour  and  burning  taste.  On  treatment  with  sodium 
methylate  it  yields  the  dimethyl  ether  C6H4(OCH3)CH2.OCH3, 
a  liquid  boiling  at  225'5°.3 

Parahydroxylenzyl  acetate,  C6H4(OH)CH2.O.C2H30,  is  formed 
in  a  similar  manner  to  the  meta-compound,  and  crystallizes 
in  yellowish  needles  melting  at  84°. 

Para-acetobenzyl  acetate,  C6H4(OC2H3O)CH2.OC2H3O,  also 
forms  yellow  needles,  melting  at  75°  (Biedermann). 

Paramethoxylenzylamine,  C6H4(OCH3)CH2.NH2,  is  obtained  by 
the  action  of  ammonia  on  the  chloride,  and  crystallizes  from  hob 
water  in  small  needles  which  have  a  strongly  alkaline  reaction 
and  melt  above  100°.  The  secondary  base,  (C8H90)2NH,  is 
formed  simultaneously  ;  it  is  less  soluble  in  water,  and  crystal- 
lizes in  plates  melting  at  32°—  33°.4 

Parahydroxybenzyl  thiocarbimide,  C6H4(OH)CH2N  zn  CS,  has 
been  already  mentioned  as  sinalbin  mustard  oil  (Part  II.  p.  392). 
It  is  a  product  of  the  decomposition  of  sinalbin,  C30H44N2S2016, 
which  crystallizes  in  small,  lustrous  needles  and  is  readily 
soluble  in  water,  slightly  in  alcohol  ;  it  is  converted  by  myrosin 
in  presence  of  water  into  sinalbin  mustard  oil,  acid  sinapin 
sulphate,  and  grape  sugar: 


,.  =  C8H7NOS  +  C^NO^SO,  +  C6H1206- 

Sinalbin  mustard  oil  is  a  non-volatile,  oily  liquid,  which  has  a 
very  sharp  taste  and  blisters  the  skin.  When  the  sulphur  is 
removed  it  is  converted  into  parahydroxyphenylacetonitril, 
C6H4(OH)CH2.CN,  which  was  considered  to  be  the  ortho- 
compound  by  Laubenheimer  and  Will.5 

1  Bertagnini  and  Cannizzaro,  Ann.  Chem.  Pharm.  xcviii.  189. 

2  Cannizzaro  and  Korner,  Ber.  Deutsch.  Chem.  Ges.  v.  436. 
»  Cannizzaro,  Ann.  Chem.  Pharm.  cxxxvii.  246. 

*  Ibid,  cxvii.  240. 

5  Ann.  Chem.  Pharm.  cxcix.  150. 


SALICYLALDEHYDE.  285 


/OH 
HYDROXYBENZALDEHYDES,  C6H4< 


ORTHOHYDROXYBENZ  ALDEHYDE,  OR    SALICYLALDEHYDE. 

2164  The  volatile  oil  of  the  flowers  of  Spircea  Ulmaria  was 
first  examined  by  Pagenstecher,  an  apothecary  of  Berne,  who 
discovered  in  it  an  acid,  the  aqueous  solution  of  which  is  coloured 
violet  by  ferric  chloride,1  and  which  was  called  "  spiroylwasser- 
sloffsdure"  C12H60(C  =  6,O  =  8)  by  Lowig,  to  whom  Pagenstecher 
intrusted  its  further  investigation.2  He  and  Weidmann  sub- 
sequently found  that  when  the  ethereal  solution  is  shaken  with 
caustic  potash,  this  is  coloured  yellow,  and  on  evaporation  of  the 
ether  an  indifferent  oil  remains  behind,  which  possesses  the 
smell  of  the  flowers  in  a  very  marked  degree,  while  if  the 
alkaline  solution  be  distilled  with  phosphoric  acid,  an  acid  oil 
passes  over  first,  followed  by  an  acid  crystallizing  in  long  needles. 
They  now  called  the  former  of  these  spirccic  acid,  or  spiroyl 
hydride,  C13H1004.3  About  the  same  time,  Piria,  working  in 
Dumas'  laboratory,  found  that  salicin  on  oxidation  with  potassium 
dichromate  and  dilute  sulphuric  acid  yields  a  volatile,  oily, 
aromatic  liquid,  which  he  called  salicyl  hydride,  C7H6O2.  This 
is  isomeric  with  benzoic  acid,  and  is  to  be  looked  upon  as  a 
hydracid,  which,  on  heating  with  caustic  potash,  yields  salicylic 
acid,  C7H603,  just  as  benzoyl  hydride  under  similar  circumstances 
yields  benzoic  acid.  The  radicals  lenzoyl,  C7H5O,  and  salicyl, 
C7H502,  are  different  oxidation  products  of  the  hydrocarbon, 
C7H5.4  Dumas,  to  whom  Pagenstecher  showed  his  preparations 
from  Spiraea,  noticed  the  great  similarity  of  the  oil  to  salicyl 
hydride  and  suggested  that  spira3ic  acid  is  identical  with  the 
latter  ;  5  this  had  already  been  proved  by  Ettling,  who  named 
the  compound  salicylous  or  spiroylous  acid.6 

The  compound  was  mistaken  for  an  acid  because  it  is  at  once 
an  aldehyde  and  a  phenol,  and  therefore  forms  salts. 

Salicylaldehyde  also  occurs   in  the  juice   of   various   plants 

1  Buchner's  Rcpert.  Pharm.  xlix.  337  ;  li.  364. 

2  Pogg.  Ann.  xxxvi.  383. 

3  Ibid.  xlvi.  57. 

4  Ann.  Chem.  Pharm.  xxix.  300,  xxx.  151. 

5  Ibid.  xxix.  306. 

8  Ibid.  xxix.  309  ;  xxxv.  241. 


280  AROMATIC  COMPOUNDS. 

belonging  to  the  genus  Spiraea,1  in  the  stem  and  root  of  Crepis 
fcetida,2  and  in  the  larvae  of  Chrysomela  populi,  which  live  on 
willows  and  poplars,  and  possess  small  openings  along  the  body 
from  which  salicyl  aldehyde  may  be  pressed  out  in  oily  drops.3 
Enz  also  obtained  it  by  distilling  the  beetle  with  water.4 

In  order  to  prepare  it,  a  mixture  of  3  parts  of  salicin  and  3 
parts  of  potassium  dichromate  is  treated  with  24  parts  of  water, 
to  which  4*5  parts  of  sulphuric  acid  diluted  with  12  parts  of 
water  are  added.  When  the  reaction  is  complete,  the  mixture 
is  distilled  until  the  distillate  passes  over  clear,  and  the  oily 
portion  then  separated  from  the  water ;  some  of  the  aldehyde 
remains  dissolved  in  the  water  and  is  extracted  by  ether.5 

If  the  distillation  be  continued  too  long,  furfurol  passes  over, 
and  all  preparations  made  from  the  aldehyde  then  become 
intensely  red-coloured  on  standing.6 

The  flower-buds  of  Spircea  Ulmaria  omy  give  a  very  small 
yield  of  salicyl  aldehyde  on  distillation  with  water,  but  a  larger 
quantity  is  obtained  when  sulphuric  acid  and  potassium  di- 
chromate are  added,  thus  showing  that  the  buds  contain  salicin.7 
Salicyl  aldehyde  is  obtained  synthetically,  along  with  the  isomeric 
parahydroxybenzaldehyde,  by  the  action  of  chloroform  on  a 
solution  of  phenol  in  caustic  soda  (Part  III.  p.  32).  They  are 
separated  by  distillation  in  steam,  with  which  the  latter  is  not 
volatile.8 

Properties. — Salicylaldehyde  is  a  liquid  with  a  pleasant  aromatic 
smell  and  a  burning  spice-like  taste ;  it  boils  at  196'5°,  solidifies 
at  20°  to  large  crystals,  and  has  a  specific  gravity  of  1*1731  at 
13'5°.  Its  aqueous  solution,  even  when  very  dilute,  is  coloured 
violet  by  ferric  chloride,  and  yellow  by  alkalis ;  it  does  not 
reduce  Fehling's  solution,9  and  forms  difficultly  soluble  com- 
pounds with  the  acid  sulphites  of  the  alkali  metals,10  this 
property  being  made  use  of  in  its  purification  (Reimer  and 
Tiemann).  It  produces  a  fine  reddish  violet  colouration  in  a 
solution  of  rosaniline  which  has  been  decolourized  by  sulphurous 
acid.11  The  aldehydes,  of  the  fatty  acids,  benzaldehyde,  &c.,  also 
give  this  reaction  (Part  II.  p.  495). 

1  "Wicke,  Ann.  Chem.  Pharm.  Ixxxiii.  175.  2  Ibid.  xci.  374. 

3  Jahresbcr.  Chem.  1850,  583.  4  Ibid.  1859,  312. 

6  Sehiff,  .47m.  Chem.  Pharm.  cl.  193.  6  Ibid.  ccx.  115. 

7  Buchner,  ibid.  Ixxxviii.  284. 

8  Reimer  and  Tiemann,  Bcr.  DeuUch.  Chem.  Ges.  ix.  824. 

9  Tollens,  ibid.  xiv.  1959. 

10  Bertagnini,  Ann.  Chem,  Pharm.  Ixxxv.  93. 

11  Schmidt,  Ber.  Deutsch.  Chem.   Ges.  xiv.  1848. 


SALICYLALDEHYDE  COMPOUNDS.  287 

As  a  phenol  it  forms  salts,  ethers,  and  ethereal  salts. 

Potassium  salicylaldehyde,  C6H4(OK)CHO  +  H2O,  is  obtained 
by  adding  caustic  potash  to  a  solution  of  the  aldehyde  in  dilute 
alcohol ;  it  crystallizes  in  light  yellow,  nacreous,  quadratic  tablets, 
which  are  readily  soluble  in  water.  The  compound  C6H4(OK) 
CHO  +  C6H4(OH)CHO  is  obtained  in  fine,  fascicular  groups  of 
needles  by  adding  the  aldehyde  to  an  alcoholic  solution  of  the 
potassium  salt. 

Barium  salicylaldehyde,  (C6H4(CHO)0)2Ba+ 2H20,  crystallizes 
in  yellow  needles,  which  are  slightly  soluble  in  cold  water. 

Copper  salicylaldehyde,  (C6H4(CHO)0)2Cu>  is  a  very  character- 
istic salt ;  when  an  aqueous  solution  of  copper  acetate  is  added  to 
a  dilute  alcoholic  solution  of  the  aldehyde,  the  liquid  becomes 
coloured  emerald  green,  and  after  a  few  minutes  deposits  spark- 
ling crystals;  the  liquid  then  presents  a  most  beautiful  appearance 
when  placecj  in  the  sunlight.  The  crystals  become  brownish- 
green  on  drying,  and  are  only  slightly  soluble  in  water  and 
alcohol  (Ettling). 

Lead  salicylaldehyde,  C6H4(CHO)OPb.OH,  is  formed  when 
basic  lead  acetate  is  added  to  an  alcoholic  solution  of  the  alde- 
hyde ;  it  is  a  yellow  precipitate  which  dissolves  on  heating,  and 
separates  out  on  cooling  in  heavy,  light-yellow  granules. 

Methyl  salicylaldehyde,  C6H4(OCH3)CHO,  is  obtained  by 
heating  the  sodium  salt  with  methyl  alcohol  and  methyl 
iodide.1  It  is  an  oily  liquid  which  possesses  a  faint  odour,  boils 
at  238°,  and,  when  perfectly  free  from  salicylaldehyde,  solidifies 
after  some  time  to  tough  prisms  melting  at  35°.  It  forms  a 
compound  with  acid  ammonium  sulphite,  which  crystallizes  in 
lustrous  prisms  and  is  readily  soluble  in  water  and  alcohol.  The 
potassium  sulphite  compound  also  crystallizes  well,  but  is  only 
slightly  soluble  in  cold  alcohol. 

Ethyl  salicylaldehyde,  C6H4(OC2H5)CHO,  was  obtained  by 
Perkin  in  a  similar  manner,  as  a  strongly  refractive  liquid  boiling 
at  247° — 249°.  It  is  also  formed  when  a  mixture  of  calcium 
formate  and  calcium  ethyl  salicylate  is  distilled,  while,  when 
calcium  salicylate  is  substituted  for  the  ethyl  compound,  only 
phenol  is  formed.2 

Benzyl  salicylaldehyde,  C6H4(OCH2.C6H5)CHO,  crystallizes 
from  boiling  alcohol  in  flat,  rhombic  prisms,  which  melt  at  46°, 

1  Perkin,  Journ.  Chem.  Soc.  xx.  418  ;  Yoswinkel,  Ber.  Deutsch.  Chem.  Ges.  xv. 
2024. 

2  Gottig,  ibid.  x.  8. 


288  AROMATIC  COMPOUNDS. 

and  have  a  faint  odour  resembling  that  of  cloves.  It  boils  above 
360°,  and  forms  an  irritating  vapour.1 

Acetyl  salicylaldehyde,  C6H4(OC2H3O)CHO,  is  formed  when 
the  sodium  salt  is  suspended  in  ether  and  treated  with  acetic 
anhydride.  It  is  extremely  soluble  in  alcohol,  crystallizes  in 
fine,  silky  needles,  melts  at  37°,  and  then  solidifies  to  a  mass 
possessing  a  satin  lustre.  Its  boiling-point  lies  at  about  253°; 
it  combines  with  the  acid  sulphites  of  the  alkali  metals.2 

Benzoyl  salicylaldehyde,  C6H4(O.CO.C6H5)CHO,  was  obtained 
by  Perkin  by  the  action  of  benzoyl  chloride  on  the  sodium 
compound.  It  is  a  thick  oily  liquid,  which  boils  above  360°, 
and  forms  the  usual  compounds  with  the  acid  sulphites  of  the 
alkali  metals.3 

2165  Eelicin,  4C6H/OC6Hn05)CHO  +  3H20,  is  formed  by 
the  action  of  dilute  nitric  acid  on  salicin.4  In  order  to  prepare 
it,  salicin  is  treated  in  flat  basins  or  plates  with  eight  times 
its  weight  of  nitric  acid  of  sp.  gr.  1/15,  containing  lower 
oxides  of  nitrogen,  which  may  be  introduced  by  the  addition  of 
a  few  drops  of  the  red,  fuming  acid.  The  helicin  is  filtered  off 
after  some  hours  and  washed  two  or  three  times  with  cold 
water.5  It  is  readily  soluble  in  hot  water  and  alcohol,  but  not 
in  ether,  and  crystallizes  in  small,  very  fine  needles,  which  have 
a  faint,  bitter  taste,  lose  their  water  of  crystallization  at  100°  and 
melt  at  175°.  It  is  not  coloured  by  ferric  chloride;  if  a  blood- 
red  colouration  be  produced,  it  contains  nitrosalicylic  acid.  It  is 
resolved  into  dextrose  and  salicylaldehyde  by  the  action  of  acids, 
alkalis  and  emulsin.  It  can  be  synthetically  prepared  by  acting 
upon  potassium  salicylaldehyde  with  an  alcoholic  solution  of 
acetochlorohydrose  :  6 

CHO 

+  C6H7C1(C2H30)405  +  4C2H5.OH  = 


C6H4<  +  4C2H5OC2H3O  +  KC1. 

\OC6Hn05 

It   is   reduced   to   salicin   by   the   action  of  sodium   amalgam 
and  water.7     It  forms  a  compound  with  acid  sodium  sulphite, 

1  Perkin,  Journ.  Chem.  Soc.  xxi.  122. 

2  Ibid.  xxi.  181. 

3  Ibid.  cxlv.  295.  4  Piria,  ibid.  Ivi.  64. 
5  Schiff,  ibid.  cliv.  14. 

8  Michael,  Amcr.  Ohcm.  Journ.  i.  309. 
7  Liseuko,  Jahresber.  Chem.  1864,  588. 


DERIVATIVES  OF  HELICIN.  289 

which  has  the  formula  C13H1607.S03HNa,  and  forms  a  dazzling 
white,  hygroscopic,  crystalline  mass.1 

When  it  is  moistened  with  one  per  cent,  nitric  acid,  dried  and 
heated  to  110° — 115°,  it  is  converted  into  parahelicin,  which  is 
without  doubt  a  polymeride;  this  substance  is  an  amorphous, 
starchy,  tasteless  powder,  which  is  scarcely  soluble  in  water  and 
alcohol,  and  has  no  action  upon  a  solution  of  rosaniline  reduced 
by  sulphurous  acid,  whereas  helicin  forms  a  reddish  violet 
crystalline  compound  with  it.  It  dissolves  in  very  dilute 
hydrochloric  acid  which  has  been  slightly  warmed,  and  is  thus 
reconverted  into  helicin.2 

Tetracetylhelicin,  C13H12(C2H30)4,  was  obtained  by  Schiff 
by  heating  helicin  with  acetyl  chloride  or  acetic  anhydride ;  it 
crystallizes  from  hot  alcohol  in  long,  silky  needles  or  prisms. 

Benzoylhelicin,  C13H15(CO.C6H5)O7.  Piria  prepared  this  com- 
pound by  the  action  of  nitric  acid  on  populin  (p.  282),3  and  Schiff 
by  heating  helicin  with  benzoyl  chloride.4  It  crystallizes  in  silky 
needles,  which  are  slightly  soluble  in  water,  more  readily  in 
alcohol.  Sodium  amalgam  and  water  reduce  it  again  to  populin ; 
on  boiling  with  water  and  magnesia  it  is  decomposed  into  helicin 
and  benzoic  acid. 

Helico'idin,  C26H34O14,  is  formed  by  dissolving  salicin  in  nitric 
acid  of  sp.  gr.  TOS5  : 

2C13H1807  +  0  =  CaftA*  +  H20. 

It  crystallizes  from  hot  water  in  needles,  and  is  very  similar  to 
helicin,  from  which  it  differs  in  being  resolved  by  acids,  &c.,  into 
dextrose,  salicylaldehyde,  and  saligenin  (Piria). 

Odacetylhelico'idin,  C26H26(C2H3O)8O14,  is  obtained  by  heating 
helicoidin  to  100°  with  acetic  anhydride;  it  is  insoluble  in  water, 
and  crystallizes  from  alcohol  in  druse-like  aggregates,  melting 
at  80°  (Schiff). 

Ortho-aldehydophenoxyacetic  acid,  C6H4(COH)OCH2.C02H,  is 
formed  when  equal  molecules  of  salicylaldehyde  and  chloracetic 
acid  are  heated  together  and  the  fused  mass  treated  with 
an  excess  of  caustic  soda  solution  of  sp.  gr.  1'2 — 1'3;  the 
mixture  is  then  heated  on  the  water-bath  until  it  has  become 
almost  solid,  the  acid  precipitated  by  hydrochloric  acid  and 

1  Schiff,  Ann.  Chcm.  Pharm.  ccx.  126. 

2  Ibid.  Ber.  Deutsch.  Chcm.  Ges.  xiv.  317. 

3  Ann.  Chem.  Pharm.  xcvi.  379. 

4  Ibid.  cliv.  23. 


290  AROMATIC  COMPOUNDS. 

re-crystallized  from  hot  water.  It  forms  large,  yellow  plates, 
which  melt  at  132°,  and  sublime  when  gradually  heated. 
Like  other  aldehydes  it  reduces  Fehling's  solution  and  am- 
moniacal  silver  solution,  and  combines  with  phenylhydra- 
zine  and  acid  sodium  sulphite.  Its  salts  are  readily  soluble 
and  crystallize  well;  its  ethyl  ether  forms  needles  melting 
at  1140.1 

2166  Orthohydroxybenzidene  compounds.     These  are  obtained 
in  a  similar  manner  to  the  benzidene  compounds. 


OrtTiohydroxyltenzidene  acetate,  C6H4<f  is  formed 

\CH(OCO.CH3)2, 

when  salicylaldehyde  is  heated  to  150°  with  acetic  anhydride; 
it  crystallizes  from  alcohol  in  thick,  hard,  transparent  tablets, 
which  melt  at  103°  —  104°,  and  distil  with  slight  decom- 
position.2 

Perkin   has  obtained  the  following  compounds  in  a  similar 
manner  : 

/OCH3  Melting-point. 

C6H4<^  ,  lustrous  prisms  .....     75° 

\CH(OCO.CH3)2 
/OC2H5 

C6H4<  ,  small  prisms  ......    88°—  89° 

\CH(OCO.CH3)2 


C6H4<(  ,  needles  or  pointed  tablets  100°— 101° 

\CH(O.CO.CH3)2 

The  last  compound  may  also  be  obtained  by  heating  salicyl- 
aldehyde to  180°  with  acetic  anhydride.3  Tolerably  concentrated 
caustic  potash  decomposes  it  into  acetic  acid  and  orthohydroxy- 
benzidene  acetate,  while  it  splits  up-  on  distillation  into  acetyl- 
salicylaldehyde  and  acetic  anhydride.4 

Orthohydroxylenzidenoxime,  or  Salicylaldoxime,  C6H4(OH) 
CH:=N.OH,  is  formed  by  the  action  of  hydroxylamine  on 
salicylaldehyde,  and  forms  white  crystals  which  dissolve  readily 
in  alcohol,  ether  and  benzene,  but  are  insoluble  in  petroleum 
spirit,  and  melt  at  57°.5  Its  compounds  resemble  those  of 
benzaldoxime  (p.  139). 

1  Rossing,  Ber.  Deutsch.  Chem.  Ges.  xvii.  2988. 

2  Perkin,  Ann.  Chem.  Pharm.  cxlvi.  371. 

3  Barbier,  Bull.  Soc.  Chim.  xxxiii.  53. 

*  Perkin,  Ann.  Chem.  Pharm.  cxlviii.  203. 
6  Lach,  Ber.  Deutsch.  Chem.  Ges.  xvi.  1782. 


HYDROSALICYL  AMIDE.  29 1 

Hydroxylenzidene-amidobenzoic  acid,  C6H4(OH)CH=:NC6H4 
C02H,  is  prepared  by  mixing  warm,  dilute,  aqueous  solutions 
of  salicylaldehyde  and  metamidobenzoic  acid.  It  crystallizes  in 
long,  yellow  needles,  which  are  very  soluble  in  alcohol  and 
benzene.  Its  aqueous  solution  gives  off  salicylaldehyde  on 
evaporation.1 

Helicin  combines  with  metamidobenzoic  acid  to  form  the 
analogous  compound  C6H4(OC6Hn05)CH:=NC6H4.C02H,  which 
crystallizes  from  alcohol  in  lustrous  plates,  melting  at  142° ; 2  it 
is  resolved  into  the  preceding  compound  and  grape  sugar  by 
heating  with  an  aqueous  solution  of  emulsin. 

Hydrosalicylamide,  N2(CH.C6H4.OH)3.  This  compound,  cor- 
responding to  hydrobenzamide  (p.  140),  was  prepared  by  Ettling 
by  the  action  of  ammonia  on  an  alcoholic  solution  of  salicylalde- 
hyde, and  named  by  him  salicylimide.3  It  forms  heavy,  light 
yellow  crystals,  melting  at  300°,  and  is  insoluble  in  water,  slightly 
in  cold,  more  readily  in  hot  alcohol,  and  decomposes  into  salicyl- 
aldehyde and  ammonia  when  heated  with  concentrated  caustic 
potash  solution  or  strong  acids.  It  absorbs  three  molecules 
of  hydrochloric  acid,  forming  a  compound  which  decomposes 
in  moist  air  into  salicylaldehyde  and  ammonium  chloride.4 

As  a  phenol  it  forms  metallic  salts ;  when  an  ammoniacal 
solution  of  copper  acetate  is  added  to  its  cold  alcoholic  solu- 
tion, the  liquid  becomes  coloured  emerald-green,  and  after  a 
few  minutes  becomes  decolourized,  cruciform  plates  being  de- 
posited, which  after  drying  have  a  strong  satin  lustre;  their 
composition  is  represented  by  the  formula  (C21H15N203)2Cu3 
(NH3)2.  They  are  almost  insoluble  in  water  and  alcohol,  and 
form  a  green  solution  in  hydrochloric  acid,  from  which  they  are 
reprecipitated  by  alkalis.  They  are  not  attacked  by  cold  caustic 
potash,  and  decomposition  only  proceeds  slowly  on  boiling ; 
salicylaldehyde  is  formed  when  it  is  heated  with  strong  acids. 

Orthobenzidenephenylhydmzine,  C6H4(OH)CH=N2H.C6H5, 
crystallizes  from  hot,  dilute  alcohol  in  yellow  needles  or  plates, 
melting  at  142° — 143°.  When  it  is  heated  with  chloracetic 
acid  a  colouring  matter,  C9H7NO3,  is  produced,  which  forms  a 
deep  bluish  green  solution  in  alcohol  and  is  coloured  cherry-red 
by  alkalis.5 

1  Schiff,  Ann.  Chem.  Pharm.  ccx.  114. 

2  Ber.  Deutsch.  Chem.   Ges.  xii.  2032. 

3  Ann.  Chem.  Pharm.  xxxv.  261. 

4  Bode,  Jahresb.  Chem.  1857,  318. 

6  Fischer,  Ber.  Deutsch.  Chem.  Ges.  xvii.  575  ;  Rossing,  ibid.  3004. 


292  AROMATIC  COMPOUNDS. 


SUBSTITUTION  PRODUCTS  OF  SALICYL- 
ALDEHYDE. 

2167  ChlorosalicylaldeJiyde,  C6H3C1(OH)CHO,  is  formed  by 
the  action  of  chlorine  on  salicylaldehyde.1  It  is  insoluble  in 
water,  and  crystallizes  from  alcohol  in  rectangular  tablets. 

Bromosalicylaldehyde,  C6H3Br(OH)CHO,  is  not  only  formed  by 
the  direct  action  of  bromine  2  but  also  when  salicylaldehyde  is 
treated  with  phosphorus  pentabromide,  the  latter  compound  act- 
ing in  the  same  manner  as  a  mixture  of  bromine  and  phosphorus 
pentabromide.3  It  crystallizes  from  ether  in  small  plates,  melt- 
ing at  98° — 99° ;  its  alcoholic  solution  is  coloured  violet  by  ferric 
chloride. 

Melting-point. 
Methylbromosalicylaldehyde,  flat  prisms  )-,-,QO     n  A  -° 

C6H3Br(OCH3)CHO.  j1 

Ethylbromosalicylaldehyde,4  sharp  prisms  ]  a^0     aQO 
C6H3Br(OC2H5)CHO.  j  b7  " 

a-Nitrosalicylaldehyde,  C6H3(NO2)(OH)CHO,  is  formed,  to- 
gether with  the  /3-compound,  by  boiling  salicylaldehyde  with 
dilute  nitric  acid ; 5  the  two  substances  are  separated  by  means 
of  their  barium  salts.  a-Nitrosalicylaldehyde  crystallizes  in 
small  yellow  prisms,  which  melt  at  105° — 107°,  while  its  barium 
salt,  (C7H4NO4)2Ba  +  2H20,  forms  slightly  soluble,  yellowish  red 
columns. 

ft-Nitrosalicylaldeliyde  forms  needles,  melting  at  123° — 125°; 
its  barium  salt,  (C7H4N04)2Ba  +  6H2O,  crystallizes  in  yellow 
prisms. 

Methylnitrosalicylaldehyde,  C6H3(N02)(OCH3)CHO,  forms  fine, 
white  needles,  melting  at  88°.6 

1  Piria,  Ann.  Chem.  Pharm.  xxx.  169  ;  Lbwig,  Bcrz.  Jahresb.  xx.  311. 

2  Piria  ;  Lowig,  Pogg.  Ann.  xlvi.  57  ;  Heberlein,  Berz.  Jahresb.  xxv.  484. 

3  Henry,  Ber.  Deutsch.  Chem.  Ges.  ii.  274. 

4  Perkin,  Ann.  Chem.  Pharm.  cxlv.  304. 

5  Mazzara,  Gazz.  Chim.  Ital.  vi.  460. 

6  Voswinkel,  Ber.  Deutsch.  Chem.  Ges.  xv.  2027 ;  Schnell,  ibid.  xvii.  1381. 


METAHYDROXYBENZALDEHYDE.  293 


METAHYDROXYBENZALDEHYDE. 

2168  This  compound  is  formed,  together  with  metahydroxy- 
benzyl  alcohol,  by  the  action  of  sodium  amalgam  on  a  faintly 
acid  solution  of  metahydroxybenzoic  acid.  It  can  be  more 
readily  obtained  from  metamidobenzaldehyde  by  treating  its 
well-cooled  solution  in  hydrochloric  acid  with  the  calculated 
quantity  of  sodium  nitrite  and  then  heating.1  It  crystallizes 
from  hot  water  in  white  needles,  melting  at  104°;  its  aqueous 
solution  is  coloured  a  faint  violet  by  ferric  chloride,  and  it  differs 
from  the  isomeric  para-compound  in  giving  a  precipitate  with 
lead  acetate. 

Methylmetahydroxylenzaldehyde,  C6H4(OCH3)CHO,  is  obtained 
by  heating  the  aldehyde  with  caustic  potash,  methyl  iodide  and 
wood-spirit.  It  is  an  oily  liquid,  which  boils  at  230°  and  has  a 
pleasant  odour. 

Acetylmetaliydroxylienzaldehyde,  C6H4(OCO.CH3)CHO,  is 
formed  by  the  action  of  acetic  anhydride  on  the  potassium 
compound  of  the  aldehyde,  and  is  an  oily  liquid,  boiling 
at  263.° 

Acetometahydroxylenzidene  acetate,  C6H4(OCO.CH3)CH(O. 
CO.CH3)9,  is  produced  when  the  aldehyde  is  boiled  with  an 
excess  of  acetic  anhydride.  It  is  slightly  soluble  in  water, 
readily  in  alcohol,  and  crystallizes  in  lustrous,  white  plates, 
melting  at  76.° 

Nitro-8ub$tttution  products.  The  three  following  compounds 
are  all  formed  by  the  direct  nitration  of  the  aldehyde ;  they 
may  be  separated  by  re -crystallization  from  hot  water,  chloro- 
form, &c. 

a-Nitrometahydroxylenzaldehyde,  C6H3(N02)(OH)CHO,  crys- 
tallizes in  yellowish  plates,  melting  at  128°,  which  are  slightly 
soluble  in  cold,  more  readily  in  hot  water,  and  readily  in 
chloroform  and  petroleum  ether. 

f$-Nitrometahydroxyl)enzaldehyde  forms  needles  which  melt  at 
166°,  and  is  more  readily  soluble  in  water  than  the  a-compound, 
but  only  very  slightly  soluble  in  chloroform  and  benzene. 

y-Nitrometahydroxylenzaldehyde  melts  at  138°,  and  crystallizes 

1  Tiemann  and  Ludwig,  Ber.  Deutsch.  Chem.  Ges.  xv.  2043  and  3052. 
250 


294  AROMATIC  COMPOUNDS. 


in  prisms,  which  dissolve  readily  in  hot  water,  chloroform  and 
benzene,  but  only  with  difficulty  in  petroleum  ether. 

When  these  compounds  are  heated  with  caustic  potash,  wood- 
spirit  and  methyl  iodide,  their  methyl  ethers,  C6H3(N02)  (OCH3) 
CHO,  are  formed  (Tiemann  and  Ludwig) ;  these  can  also  be 
obtained  by  the  nitration  of  metamethoxybenzaldehyde.1 

a-Orthonitroniethylmetahydroxybenzaldehyde  crystallizes  from 
chloroform  in  thick,  yellow  prisms,  melting  at  107°. 

(3-Orthonitromethylmetahydroxybenzaldehyde  forms  white  plates 
or  needles,  which  melt  at  82°— 83°.' 

These  bodies  are  known  to  be  orthonitro-compounds  because 
they  give  the  indigo  reaction  (p.  146). 

Metanitromethylmetahydroxybenzaldehyde  crystallizes  in  needles 
or  prisms,  and  melts  at  98°. 

ParanitrometTiylmetahydroxybenzaldehyde  was  obtained  by 
Ulrich  by  the  oxidation  of  paranitromethoxycinnamic  acid ;  it 
crystallizes  in  hair-like  needles  and  melts  at  62°. 


PARAHYDROXYBENZALDEHYDE. 

2169  This  body  was  first  prepared  by  Bucking  by  heating  the 
methyl  ether,  anisaldehyde,  with  hydrochloric  acid.2  It  may  be 
synthetically  obtained  by  the  action  of  chloroform  on  an  alkaline 
solution  of  phenol,  salicylaldehyde  being  formed  at  the  same  time. 

In  order  to  prepare  it,  30  parts  of  chloroform  are  gradually 
added  to  a  solution  of  20  parts  of  phenol  in  120  parts  of  water 
heated  to  50° — 60° ;  the  liquid  becomes  coloured  blue  and  then 
deep  red,  a  considerable  rise  of  temperature  taking  place,  the 
use  of  an  inverted  condenser  being  thus  rendered  necessary. 
The  mixture  is  finally  boiled  for  half  an  hour,  the  excess  of 
chloroform  distilled  off,  an  excess  of  sulphuric  acid  added,  and 
the  whole  distilled  in  steam,  salicylaldehyde  passing  over  along 
with  any  free  phenol,  from  which  it  is  subsequently  separated  by 
means  of  acid  sodium  sulphite.  The  residual  liquid  is  filtered  while 
hot  from  the  deep  red  coloured  resin  which  is  formed,  and  after 
cooling  is  extracted  with  ether ;  on  evaporation  of  the  ether,  the 
parahydroxybenzaldehyde  is  left  behind,  and  is  then  re-crystall- 
ized from  boiling  water.3  It  is  slightly  soluble  in  cold,  more  readily 

1  M.  Ulrich,  Ber.  Deutsch.  Chem.  Ges.  xviii.  2571.  2  Ibid.  ix.  527. 

3  Reimer  and  Tiemann,  ibid.  ix.  824  ;  Tiemann  and  Herzfeld,  ibid.  x.  63. 


PARAHYDROXYBENZALDEHYDE.  295 

in  hot  water,  and  readily  in  alcohol,  ether,  &c.,  and  crystallizes 
in  fine  needles,  which  have  a  faint  but  pleasant  aromatic  odour, 
melt  at  115° — 116°,  and  sublime  unaltered.  Its  aqueous  solu- 
tion is  coloured  a  dirty  violet  by  ferric  chloride ;  if  its  ethereal 
solution  be  shaken  up  with  a  solution  of  acid  sodium  sulphite, 
combination  ensues,  but  the  double  compound  is  readily  soluble. 
Its  solution  is  not  easily  attacked  by  oxidizing  agents,  but  it  is 
converted  into  parahydroxybenzoic  acid  by  fusion  with  caustic 
potash  at  a  low  temperature. 

Methylparahydroxybenzaldeliyde,  C6H4(OCH3)CHO.  Cahours 
prepared  this  compound  by  the  oxidation  of  oil  of  anise  seed,1 
while  Cannizzaro  and  Bertagnini  obtained  it  by  oxidizing  anise 
alcohol  (p.  284),  and  named  it  anisaldehyde.2  Piria  then  showed 
that  it  is  also  formed  by  distilling  a  mixture  of  calcium  formate 
and  calcium  anisate  (methylparahydroxybenzoate)  ; 3  and  Tie- 
mann  and  Herzfeld  obtained  it  by  heating  parahydroxybenz- 
aldehyde  with  methyl  iodide,  wood -spirit  and  caustic  potash. 

It  may  be  most  readily  prepared  from  oil  of  anise,  which 
consists  for  the  most  part  of  anethol,  C3H5.C6H5.OCH3,  the 
methyl  ether  of  allylphenol.  One  part  of  this  is  brought  into  a 
cold  solution  of  2  parts  of  potassium  dichromate,  3  parts  of 
sulphuric  acid,  and  8  parts  of  water.  As  soon  as  the  temperature 
ceases  to  rise,  the  mixture  is  diluted  with  half  its  volume  of 
water  and  distilled,  the  quantity  of  liquid  in  the  distilling  flask 
being  kept  at  its  original  volume  by  the  gradual  addition  of 
water.  The  distillate  is  repeatedly  rectified,  the  aldehyde 
coming  over  in  the  first  portions,  which  are  then  shaken  up  with 
a  concentrated  solution  of  acid  sodium  sulphite.  The  crystals, 
which  separate  after  some  time,  are  washed  with  alcohol  and 
decomposed  by  carbonate  of  soda  solution.4 

Anisaldehyde  is  a  liquid  which  has  an  aromatic  odour,  boils  at 
247° — 248°,  and  dissolves  slightly  in  cold,  more  readily  in  hot 
water ;  it  readily  takes  up  oxygen  from  the  air  and  is  converted 
by  alcoholic  potash  into  a  mixture  of  anise  alcohol  and  anisic 
acid.  When  heated  with  dilute  hydrochloric  acid  to  200°,  it 
decomposes  into  parahydroxybenzaldehyde  and  methyl  chloride 
(Bucking). 

Acetylparahydroxylenzaldehyde,  C6H4(OCO.CH3)CHO,  is  ob- 
tained by  dissolving  2  parts  of  parahydroxybenzaldehyde  and 
1  part  of  caustic  potash  in  water,  evaporating  and  treating  the 

1  Ann.  Chem.  Pkarm.  Ivi.  307.  2  Ibid,  xcviii.  189. 

3  ibid.  c.  105.  4  Rossel,  ibid.  cli.  28. 


296  AROMATIC  COMPOUNDS. 

residue  with  acetic  anhydride  in  presence  of  ether  (Tiemann 
and  Herzfeld). 

It  is  also  formed  by  the  action  of  acetic  anhydride  on  the 
aldehyde,1  and  is  a  liquid,  boiling  at  264° — 265°,  which  forms  an 
almost  insoluble  compound  with  acid  sodium  sulphite. 

Acetylparakydroxybenzidene  acetate,  C6H4(OCO.CH3)CH(OCO. 
CH3)2,  is  prepared  by  heating  the  aldehyde  with  three  times  its 
weight  of  acetic  anhydride.  It  is  readily  soluble  in  hot  water 
and  alcohol,  and  crystallizes  from  ether  in  flat  prisms,  melting 
at  93°— 94°  (Tiemann  and  Herzfeld). 

Parahydroxybenzaldoxime,  C6H4(OH)CH=:NOH,  forms  odour- 
less, white  needles.2 

Chloroparahydroxylenzaldehyde,  C6H3C1(OH)CHO,  crystallizes 
from  hot  water  in  silky  needles  melting  at  148° — 149° ;  its  aqueous 
solution  is  coloured  violet  by  ferric  chloride. 

Bromoparahydroxybenzaldehyde,  C6H3Br(OH)CHO,  is  almost 
insoluble  in  water,  crystallizes  from  alcohol  in  long,  strongly 
refractive  needles,  melting  at  179°-— 180°,  and  does  not  give  any 
colouration  with  feme  chloride. 

lodoparahydroxylenzaldeliyde,  C6H3I(OH)CHO,  is  formed 
when  parahydroxybenzaldehyde  is  boiled  with  iodine  and  dilute 
alcohol.  It  is  slightly  soluble  in  water,  readily  in  alcohol,  and 
separates  from  chloroform  in  white  crystals,  melting  at  198° — 
199°.  On  heating  with  caustic  potash  it  yields  protocatechuic 
acid.3 

Nitroparahydroxylenzaldehyde,  C6H3(N02)(OH)CHO.  Maz- 
zara  obtained  this  substance  by  boiling  the  aldehyde  with  dilute 
sulphuric  acid,4  and  Herzfeld  by  adding  concentrated  nitric 
acid  to  a  solution  of  parahydroxybenzaldehyde  in  concentrated 
sulphuric  acid.5  It  is  soluble  in  boiling  water  and  alcohol,  and 
crystallizes  in  yellowish  needles  melting  at  139° — 140°.  Its 
aqueous  solution  gives  a  fugitive  red  colouration  with  ferric 
chloride.  It  decomposes  carbonates ;  the  potassium  salt,  C6H3 
(NO2)(OK)CHO  +  H20,  forms  golden-yellow  tablets. 

1  Barbier,  Bull.  Soc.  CMm.  xxxiii.  54. 

2  Lach,  Ber.  Deutsch.  Chem.  Ges.  xvi.  1785. 

3  Herzfeld,  ibid.  x.  2196. 

4  Gfaz.  Chim.  Ital.  vii.  285. 

6  Ber.  Dcutsch,  Chem.  Ges.  x.  1269. 


SALICYLIC  ACID.  297 


/OH 
HYDROXYBENZOIC  ACIDS,  C6H4< 

XC02H. 

OETHOHYDROXYBENZOIC  ACID,  OR  SALICYLIC  ACID. 

2170  The  history  of  this  important  substance  is  of  special 
interest  because  its  genetic  relations  to  the  benzoyl  and  cinnamyl 
groups  and  to  indigo  blue  were  known  at  a  very  early  period. 
Piria,  who  prepared  it  in  1838,  by  heating  the  aldehyde  with 
caustic  potash,1  pointed  out  that  the  radicals  benzoyl  and  salicyl 
are  different  oxidation  products  of  the  hydrocarbon  or  radical 
C7H5  (p.  285).  Marchand  2  and  Gerhardt  3  found  that  it  is  also 
formed  when  salicin  is  melted  with  potash,  and  is  converted  by 
dilute  nitric  acid  into  nitrosalicylic  acid,  which  is  identical  with 
indigotic  or  anilotic  acid,  a  substance  obtained  by  the  action  of 
nitric  acid  on  indigo  which  had  long  been  familiar  to  chemists. 
This  compound  on  fusion  with  potash  at  a  low  temperature 
yields  anthranilic  acid  (p.  237),  while  Cahours,  by  carrying  out 
the  operation  at  a  higher  temperature,  obtained  salicylic  acid ; 4  it 
was  obtained,  together  with  acetic  acid,  in  a  similar  manner 
from  cumaric  acid  by  Delalande,  who  remarked  that  this  latter 
compound  bears  the  same  relation  to  cinnamic  acid  as  salicylic 
to  benzoic  acid.5  Ettling,  who  prepared  salicylic  acid  by 
oxidizing  its  aldehyde  with  potassium  dichromate  and  sulphuric 
acid,  found  that  it  can  also  be  obtained  by  heating  the  copper 
salt  of  this  or  of  benzoic  acid,  and  is  therefore  an  oxidation 
product  of  the  latter.6  Gerhardt  had  previously  observed  that 
salicylic  acid  decomposes  on  heating  into  phenol  and  carbon 
dioxide,  just  as  anthranilic  acid  is  split  up  into  aniline  and 
carbon  dioxide.  A  series  of  relations  was  thus  established 
among  the  following  compounds: 

Benzene  Benzoic  acid  Cinnamic  acid 

C6H6  C7H6O2  C9H8O2 

Phenol  Salicylic  acid  Cumaric  acid 

CeH60  C7H60S  C9H803 

Aniline  Anthranilic  acid 

C6H7N  C7H7N02 

1  Ann.  Chim.  Phys.  Ixix.  298  ;  Ann.  Chem.  Pharm.  xxx.  1 65. 

2  Journ.  Prakt.   Chem.  [1]  xxvi.  396.  3  Ann.  Chem.  Pharm.  xlv.  19. 
*  Ibid.  lii.  343.                 s  Ibid.  xlv.  336.  6  Ibid.  liii.  77. 


298  AEOMATIC  COMPOUNDS. 

Hofmann  found  that  aniline  is  converted  into  phenol  by  the 
action  of  nitrous  acid,  and  suggested  that  anthranilic  acid  would 
probably  yield  salicylic  acid  when  treated  in  a  similar  manner, 
this  suggestion  being  experimentally  verified  by  Gerland.1 

Salicylic  acid  was  obtained  synthetically  by  Kolbe  and  Laute- 
mann  by  the  action  of  carbon  dioxide  on  a  mixture  of  phenol 
and  sodium.2  The  former  chemist  found  that  it  is  also  formed 
when  carbon  dioxide  is  passed  over  heated  sodium  phenate,  half 
of  the  phenol  being  set  free  : 3 

/ONa 

2C6H5.ONa  +  CO2  =  C6H  /  +  C6H5OH. 

\C02Na 

Ethyl  salicylate  may  be  prepared  by  the  action  of  sodium  on 
a  mixture  of  phenol  and  ethyl  chloroformate  : 4 

/OH 

C6H5.ONa  4-  C1C02.CLH6  =  C6H4<  +  NaCl. 

XC02.C2H5 

The  acid  is  also  formed,  together  with  parahydroxybenzoic 
acid,  when  a  mixture  of  tetrachloromethane  and  phenol  is  heated 
to  100°  with  alcoholic  potash  (Part  III.  p.  32).5 

It  may  also  be  obtained  by  fusing  orthocresol,6  toluene- 
orthosulphonic  acid,7  &c.,  with  caustic  potash,  as  well  as  by 
heating  copper  benzoate  to  180°  with  water,8  and  when  sodium 
is  allowed  to  remain  in  contact  with  ethyl  succinate  for  a  long 
time.9  It  has  also  been  observed  as  a  product  of  the  action 
of  hydrogen  dioxide  on  a  solution  of  benzoic  acid  in  sulphuric 
acid.10 

Salicylic  acid  also  occurs  in  nature.  Lb'wig  and  Weidmann 
detected  it  in  the  flowers  of  Spircea  Ulmaria,  accompanied  by 
salicylaldehyde,  but  did  not  actually  identify  it.  Its  methyl 
ether  is  contained  in  the  ethereal  oils  of  the  various  species  of 
Gaultheria. 

21  j  i  It  was  formerly  prepared  exclusively  from  the  winter- 

1  Ann.  Chem.  Pharm.  Ixxxvi.  147. 

2  Ibid.  cxv.  201. 

3  J&urn.  Prakt.  Chem.  [2]  x.  89. 

4  Wilm  and  Wischin,  Zcitschr.  Chem.  1868,  6. 

3  Reimer  and  Tiemann,  Ber.  Deutsch.  Chem.  Ges.  ix.  1285. 

6  Earth,  Ann.  Chem.  Pharm.  cliv.  360. 

7  Wolkow,  Zeitschr.  Chem.  1870,  326. 

8  Smith,  Amer.  Chem.  Journ.  ii.  338. 

9  Herrmann,  Ber.  Deutsch.  Chem.  Ges.  x.  646. 
10  Hanriot,  Compt.  Rend.  cii.  1250. 


SALICYLIC  ACID. 


green  oil  obtained  from  Gaulthcria  procumbms  by  saponifying 
with  potash  and  decomposing  the  product  with  hydrochloric 
acid.  It  is  now  manufactured  by  Kolbe's  process. 

The  calculated  quantity  of  pure  phenol  is  dissolved  in  strong 
caustic  soda  solution,  the  whole  evaporated  to  dryness  and  the 
residue  rubbed  into  a  dry  powder  ;  this  is  then  gradually  heated 
up  to  180°  in  a  metal  retort  in  a  current  of  carbon  dioxide  which 
has  been  previously  warmed.  After  some  time  phenol  com- 
mences to  distil  over,  and  is  subsequently  given  off  in  larger 
quantity;  the  temperature  is  then  raised  to  200°,  and  the 
operation  continued  until  no  more  phenol  comes  over.  The 
residue  is  dissolved  in  water  and  fractionally  precipitated  with 
hydrochloric  acid  ;  resinous  and  colouring  matters  are  first  thrown 
down,  followed  by  tolerably  pure  acid,  which  is  re-crystallized 
from  water  and  purified  by  distillation  with  superheated  steam.1 

According  to  another  patented  process,  carbonyl  chloride, 
which  is  now  manufactured  on  a  large  scale,  is  passed  into  a 
mixture  of  sodium  carbonate  and  phenate  heated  to  140°,  the 
temperature  being  finally  raised  to  2000.2 

Various  hypotheses  were  proposed  to  explain  the  course  of 
the  reaction  which  occurs  when  sodium  phenate  is  heated  in  a 
stream  of  carbon  dioxide.  The  correct  explanation  was  found 
by  R.  Schmitt.3  Pure  dry  sodium  phenate  absorbs  carbon 
dioxide  with  formation  of  sodium  phenylcarbonate,CoH.5O.CQ.O]$a,, 
as  a  white  powder  which  is  instantly  decomposed  by  water, 
phenol  and  sodium  bicarbonate  being  formed.  When  heated  in 
a  closed  tube  to  120°  —  130°,  it  is  converted  quantitatively  into 
monosodium  salicylate.  In  Kolbe's  reaction,  this  complete  decom- 
position does  not  take  place,  and  the  monosodium  salicylate 
reacts  with  the  sodium  phenate  at  a  higher  temperature,  phenol 
being  liberated  : 

O.C6H5  C6H4.OH 


NaO.C6H5  +  CO9     = 


CCXNa  CO0Na. 


C6H4.OH  C6H4ONa 

|  +  NaO.C6H5  =    |  +C6H5.OH. 

C02Na  C02Na 

Salicylic  acid  is,  therefore,  best  prepared  by  bringing  abso- 
lutely dry  sodium  phenate  into  an  autoclave,  pumping  in  rather 

1  Rautert,  Compt.  Rend.  viii.  537. 

2  Ibid,  xviii.  Ref.  90. 

3  Journ.  Prakt.  Chcm.  [2]  xxxi.  397. 


300  AROMATIC  COMPOUNDS. 

more  than  the  calculated  quantity  of  carbon  dioxide,  the  mass 
being  kept  cool  during  the  absorption,  or,  better,  adding  it  in 
the  solid  form,  agitating  for  some  time  and  then  heating  to 
120°— ISO0.1 

2172  Salicylic  acid  has  a  slightly  acid,,  astringent  and  at  the 
same  time  sweet  taste ;  it  dissolves  slightly  in  cold,  more  readily 
in  hot  water,  from  which  it  crystallizes  in  fine  needles,  while  it 
is  deposited  in  monoclinic  prisms  from  an  alcoholic  solution 
which  is  allowed  to  evaporate  spontaneously. 

100  parts  of  water  dissolve  at : 

0°  15°  100° 

0-085  0-225  7-925  parts. 

Absolute  alcohol  and  ether  dissolve  about  half  their  weight  of 
the  acid ; 2  it  is  also  readily  soluble  in  chloroform,  differing  in 
this  respect  from  its  isomerides,  and  is  dissolved  by  solutions 
of  the  acetates  and  citrates  of  the  alkali  metals.3 

Its  aqueous  solution  is  coloured  deep  violet  by  ferric  chloride ; 
free  acids,  especially  acetic  and  hydrochloric  acids,  hinder  the  re- 
action.4 It  prevents  the  precipitation  of  copper  salts  by  alkalis, 
while  its  isomerides  have  not  this  property.5  Strong  boiling 
nitric  acid  converts  it  into  picric  acid,  and  chromic  acid  oxidizes 
it  to  water,  carbon  dioxide  and  a  little  formic  acid.6 

It  melts  at  155° — 1560,7  and  sublimes  on  gradual  heating,  but 
partially  decomposes  into  carbon  dioxide  and  phenol  when 
rapidly  heated.  It  is  completely  split  up  when  heated  to 
250° — 260°  for  two  hours  in  a  sealed  tube ;  on  cooling,  the 
compound  of  these  two  substances,  which  has  already  been 
described,  separates  out  (Part  III.  p.  102).8  This  decomposition 
also  occurs  when  the  acid  is  heated  for  a  long  time  to  220° — 2.30° 
with  water,  and  more  rapidly  in  presence  of  hydrochloric -acid  at 
140° — 1500.9  Sodium  amalgam  only  acts  upon  it  in  acid  solu- 
tion ;  a  resinous  substance,  probably  saliretin,  being  formed.10  In 
order  to  test  the  purity  of  salicylic  acid,  a  piece  the  size  of  a  pea 

Bcr.  Deutsch.  Chem.  Gcs.  xvii.  Kef.  624  ;  Schmitt,  loc.  cit. 
On  Solubility,  &c.,   see  Ost,   Juurn.  Prakt.  Chem.  [2]  xvii.  232  ;  Bourgoin, 
Bull.  Soc.  Ghim.  xxix.  247  ;  xxxi.  57. 

R  other,  Pharm.  Journ    Trans.  1886,  328. 

Pagliani,  Bcr.  Deutsch.  Chem.  Gcs.  xii.  385.  5  Weith,  ibid.  ix.  342. 

Kraut,  Ann.  Chem.  Pharm.  cl.  9.  7  Hiibner,  ibid,  clxii.  74. 

Klepl,  Journ.  Prakt.  Chem.  [2]  xxv.  464. 
Grabe,  ibid,  cxxxix.  143. 
10  Velden,  Journ.  Prakt.  Chem.  [2]  xv.  164. 


THE  SALICYLATES.  301 


is  ground  up  with  five  ccs.  of  concentrated  sulphuric  acid,  in 
which  it  should  form  a  perfectly  colourless  solution.1  Its  alcoholic 
solution  evaporated  on  a  watch-glass  should  yield  perfectly 
clear  and  colourless  crystals  :  if  they  are  yellow  or  brown,  the 
sample  contains  admixed  resins  or  colouring  matters,  while  if 
they  are  pink  or  violet,  iron  is  present. 

As  salicylic  acid  decomposes  so  readily  into  carbon  dioxide  and 
phenol,  Kolbe  considered  that  it  would,  like  the  latter,  be  a 
powerful  antiseptic,  and  subsequently  verified  this  conclusion  by 
experiment.  It  has  very  rapidly  come  into  favour  both  for 
technical  and  household  purposes,  and  is  preferable  to  phenol 
because  it  has  no  smell  and  is  not  poisonous.  Its  isomerides, 
according  to  Kolbe,  are  not  antiseptics.2  Salicylic  acid  is  also 
employed  in  medicine,  both  for  external  and  internal  application. 
Several  physicians  have  observed  that  the  acid  prepared  from 
winter-green  oil  acts  more  powerfully  than  that  obtained 
artificially,  but  this  may  possibly  be  due  to  the  fact  that  the 
acid  which  first  came  into  the  market  contained  a  considerable 
amount  of  impurity.3 

2173  The  Salicylates.  Salicylic  acid  was  first  thought  to  be  a 
monobasic  acid,  but  was  afterwards  regarded  as  dibasic.  Piria 
observes  on  this  point :  "  Salicylic  acid  differs  in  a  most  striking 
manner  from  other  monobasic  acids  in  forming  acid  ethers,  which 
are  more  fitly  compared  with  the  acid  ethers  of  polybasic  acids 
than  with  the  neutral  ethers.  In  the  course  of  researches  which 
I  have  instituted  upon  this  question,  I  have  succeeded  in  finding 
the  cause  of  this  exception,  or  rather  in  showing  that  the  behaviour 
of  this  acid  is  not  exceptional.  Salicylic  acid,  which  has 
hitherto  been  looked  upon  as  monobasic,  is  actually  dibasic,  and 
very  markedly  so ;  it  forms  salts  with  two  equivalents  of  a  base 
so  readily  that  it  is  singular  that  they  have  remained  so  long 
unnoticed.  In  the  following,  I  shall  call  salts  containing  one 
equivalent  of  base,  which  have  been  previously  described,  acid 
salicylates,  and  those  discovered  by  me,  containing  two  equivalents 
of  base,  neutral  salicylates."  4 

This  view  was  accepted  by  most  chemists,  but  Kolbe  con- 
sidered it  to  be  a  monobasic  hydroxy-acid.  Further  researches 
have  shown  that  it  is  both  a  monobasic  acid  and  a  phenol,  and 

1  Hager,  Frcsenius'  Zeitschr  xvi.  259. 

2  Journ.  Prakt.  Chem.  [2]  xi.  9. 

3  Williams,  Yearbook  of  Pharm.  1884,  424. 

4  Ann.  Chem.  Pharm.  xciii.  262. 


302  AROMATIC  COMPOUNDS. 

therefore  contains  two  hydrogen  atoms  which  are  easily  replaced 
by  metals.  The  salts  thus  obtained  are  usually  called  basic 
salicylates,  while  those  formed  by  the  replacement  of  the 
hydrogen  of  the  carboxyl  group  are  known  as  normal  salicylates. 
The  latter  have  recently  been  carefully  examined  by  Milone.1 

Potassium  salicylate,  C6H4(OH)CO2K,  is  obtained  by  dissolving 
the  acid  in  potassium  carbonate  solution,  evaporating  and  ex- 
tracting the  residue  with  alcohol.  It  is  deposited  in  needles  on 
the  spontaneous  evaporation  of  its  aqueous  solution.  When 
heated  to  210° — 220°,  it  decomposes  quantitatively  into  basic 
potassium  parahydroxybenzoate,  phenol  and  carbon  dioxide  : 

/OH  /OK 

2C6H/  =  C6H4<(  +  C6H5.OH  +  CO2. 

\C08K  \C02K 

If  a  solution  of  one  molecule  of  the  acid  and  two  molecules 
of  caustic  potash  be  evaporated  to  dryness,  and  the  residue 
heated  to  220°,  the  basic  salt  of  parahydroxybenzoic  acid  is  also 
formed,  together  with  phenol : 

/OK  /OK 

2C6H4<(  +  H90  =  C6H4<;  +  C6H6.OH  +  K2C03. 

XC02K  \C02K 

If,  however,  three  or  more  molecules  of  potash  are  employed, 
the  salicylic  acid  is  not  changed  ;  if  four  are  taken,  complete 
decomposition  into  carbon  dioxide  and  phenol  sets  in  at  300°, 
while  in  the  presence  of  six  molecules,  the  acid  remains  quite 
unaltered  even  at  this  temperature.2  Rubidium  salicylate 
behaves  in  a  precisely  similar  manner  on  heating.3 

Sodium  salicylate,  C6H4(OH)CO2Na,  forms  silky  tablets  or  a 
crystalline  powder,  and  has  an  unpleasant  sweet  taste.  It 
dissolves  in  its  own  weight  of  water  and  is  used  in  medicine. 
On  heating  to  above  200°,  phenol  and  carbon  dioxide  are  given 
off,  the  basic  salt  remaining  behind,  but  not  a  trace  of  the  para- 
acid  is  formed  even  at  300°.  When  salicylic  acid  is  heated  to 
this  temperature  with  four  molecules  of  caustic  soda,  it  decom- 
poses into  phenol  and  carbon  dioxide,  while  if  eight  molecules 
are  added  the  greater  portion  of  it  remains  unaltered  (Ost). 

1  Gaz.  Chim.  Ital.  xv.  219. 

2  Ost,  Journ.  Prakt.  Chem.  [2]  xi.  391. 

3  v.  d.  Velden,  ibid.  [2]  xv.  151. 


THE  SALICYLATES.  303 


Inversely,  sodium  parahydroxybenzoate  is  converted  into 
basic  sodium  salicylate,  phenol  and  carbon  dioxide,  when  it  is 
heated  to  290°  in  a  current  of  carbon  dioxide,1  while  hydroxy- 
isophthalic  acid,  C6H3(OH)(CO2H)2,  and  hydroxytrimesic  acid, 
C6H2(OH)(C02H)3,  are  formed  at  temperatures  above  300°. 

When  equal  molecules  of  salicylic  acid  and  its  normal  salt 
are  dissolved  in  alcohol  and  the  solution  concentrated,  hard, 
clear  crystals  of  C7H603  -f  C7H5NaO3  are  obtained,  which  are 
converted  by  water  into  pseudomorphs  of  salicylic  acid.2 

Lithium  salicylate  is  converted  into  the  basic  salt  at  300° 
without  any  formation  of  parahydroxybenzoic  acid. 

Thallium  salicylate,  C6H4(OH)C02T1,  is  obtained  by  neutra- 
lizing the  acid  with  thallium  carbonate ;  its  hot,  concentrated 
solution  deposits  coarse  needles  on  cooling.  If  the  calculated 
quantity  of  thallium  hydroxide  be  added  to  the  solution,  the 
basic  salt,  C6H4(OT1)CO2T1,  separates  out  in  yellow,  nacreous, 
rhombic  tablets,  which  are  only  very  slightly  soluble  in  water. 
This  compound  is  also  formed,  together  with  phenol,  when  the 
normal  salt  is  heated  to  300°,  while  at  a  higher  temperature  the 
salicylic  acid  is  partially  converted  into  parahydroxybenzoic 
acid  and  hydroxyisophthalic  acid  (v.  d.  Velden). 

Ammonium  salicylate,  2C6H4(OH)CO2NH4  +  H20,  forms 
readily  soluble,  monoclinic  crystals ;  when  heated  in  a  current  of 
ammonia  it  decomposes  into  phenol  and  ammonium  carbonate. 
The  methylamine  and  aniline  salts  behave  in  a  similar  manner, 
while  tetra-ethylammonium  salicylate  decomposes  on  heating 
into  tri-ethylamine  and  ethyl  salicylate.3 

Calcium  salicylate,  (C7H503)2Ca  +  2H2O,  is  readily  soluble  in 
water,  and  crystallizes  in  octohedra ;  when  it  is  heated  with  a 
solution  of  calcium  sucrate,  or  when  salicylic  acid  is  heated  with 
an  excess  of  milk  of  lime,  the  basic  salt,  C7H403Ca  +  H2O,  is 
formed  as  a  sandy,  crystalline  powder,  which  is  almost  insoluble 
in  water  and  has  an  alkaline  reaction  (Piria). 

Barium  salicylate,  (C7H5O3)2Ba  +  H2O,  is  obtained  by  boiling 
the  acid  with  water  and  barium  carbonate ;  it  crystallizes  in 
stellate  aggregates  of  silky  needles.  When  baryta  water  is 
added  to  its  boiling  concentrated  solution.,  the  slightly  soluble, 
alkaline,  basic  salt,  C7H4O3Ba  +  2H2O,  separates  out  in  small 
plates  or  needles. 


*  Kupferberg,  Journ.  Prakt.  Chem.  [2]  xiii.  104. 

2  Hofraann,  Arch.  Pharm.  [3]  xii.  226. 

3  Kupferberg,  Journ.  Prakt.  Chem.  [2]  xvi.  437. 


304  AROMATIC  COMPOUNDS, 

Lead  salicylate,  (C7H5O3)2Pb  4-  H2O,  separates  from  boiling 
water  in  transparent  crystals  ;  when  it  is  boiled  with  water,  or 
when  lead  acetate  is  added  to  its  hot  solution,  a  slightly  soluble, 
crystalline  precipitate  of  C7H4O3Pb  is  formed.  If,  however, 
ammonia  be  added,  and  the  solution  boiled,  the  basic  salt, 
2(C7H403)Pb  +  3PbO,  is  formed  ;  it  is  a  light  powder  consisting 
of  micaceous  plates. 

Copper  salicylate,  (C7H5O3)2Cu  +  4H2O,  is  best  prepared  by 
decomposing  the  barium  salt  with  copper  sulphate  ;  it  crystal- 
lizes in  long,  bluish  green  needles,  which  are  readily  soluble  in 
water,  and  on  boiling  with  it  form  the  basic  salt,  C7H4O3Cu  -f  H2O, 
which  is  a  yellowish  green  powder. 

Basic  copper  potassium  salicylate,  C7H4O3Cu  -f-  C7H403K2  + 
4H2O,  is  formed  by  adding  salicylic  acid  to  a  solution  of  copper 
tartarate  in  tolerably  strong  caustic  potash;  a  green  mass  of 
crystals  is  formed,  which  is  dried  on  a  porous  plate  and  re- 
crystallized  from  a  little  lukewarm  water.  Small,  emerald-green, 
rhombic  tablets  are  thus  obtained,  which  are  insoluble  in  alcohol, 
and  form  a  dark  blue  solution  in  caustic  potash.  When  the 
aqueous  solution  is  boiled  it  becomes  colourless  and  deposits 
black  copper  oxide.  Barium  chloride  produces,  on  standing,  a 
green,  crystalline  precipitate  of  C7H4O3Cu  +  C7H4O3Ba  +  4H2O. 

Silver  salicylate,  C7H5O3Ag,  is  a  precipitate  which  crystallizes 
from  boiling  water  in  very  lustrous,  transparent  needles. 

Borondisalicylic  acid,  B(OH)(OC6H4.C02H)2,  is  not  known  in 
the  free  state  ;  its  sodium  salt  is  formed,  along  with  free  boric 
acid,  when  four  molecules  of  salicylic  acid  are  added  to  a  boiling 
solution  of  one  molecule  of  borax,  as  well  as  by  dissolving  a 
mixture  of  equal  molecules  of  boric  acid,  salicylic  acid  and 
sodium  salicylate  : 

/OH 
HO  -  B<          +  HO.C6H4.C02H  +  HO.C6H4.C02Na  = 


/OC6H4.C02H 
HO-B<  +2H20. 

\OC6H4.C02Na 

It  forms  crystalline  crusts  and  is  readily  soluble  in  hot  water 
and  alcohol.  Its  aqueous  solution  turns  turmeric  paper  brown, 
reddens  litmus  paper,  and  is  coloured  violet  by  ferric  chloride  ; 
hydrochloric  acid  gives  a  precipitate  of  salicylic  acid.  Several 


METHYLSALICYLIC  ACID.  305 

other  of  its  salts  have  been  prepared  ;  its  barium  salt  is  only 
slightly  soluble  in  boiling  water.1 

2174  Methyl  salicylate,  C6H4(OH)C02.CH3.  Cahours,  in  1843, 
found  that  winter-green  oil,  obtained  from  Gaultheria  procumbens 
(Canadian  tea),  one  of  the  Ericaceae,  which  occurs  abundantly  in 
the  north  of  the  United  States  and  in  Canada,  consists  of  this 
compound  together  with  small  quantities  of  a  terpene,  and  he 
prepared  the  ether  by  distilling  salicylic  acid  with  wood-spirit 
and  sulphuric  acid  in  order  to  compare  the  two  products.2  Since 
as  a  phenol  it  forms  metallic  salts,  it  was  called  gaultheriaic 
acid  and  methylsalicylic  acid,  the  latter  name  being  now  given 
to  the  following  compound. 

The  ethereal  oils  of  Gaultheria  punctata  and  G-aultheria 
leucocarpa,  which  grow  on  the  summits  of  extinct  volcanoes 
in  Java,3  and  of  Andromeda  Lechenaultii,  one  of  the  Ericaceae, 
which  occurs  abundantly  in  the  Neilgherry  Mountains  in  India,4 
consist  almost  entirely  of  methyl  salicylate. 

It  is  a  liquid  with  a  pleasant,  refreshing  odour,  and,  boils  at 
217°.  Winter-green  oil  is  largely  used  in  America  as  a  perfume  ; 
that  obtained  artificially,  by  heating  salicylic  acid  with  methyl 
alcohol  and  sulphuric  acid,  does  not  possess  the  fine  odour  of  the 
natural  product. 

Methylsalicylic  acid,  C6H4(OCH3)CO2H.  Cahours  obtained 
the  methyl  ether  of  this  compound  by  the  action  of  methyl 
iodide  and  caustic  potash  on  winter-green  oil.  It  is  a  liquid 
boiling  at  244° — 246°  (Schreiner).  In  order  to  prepare  the  acid, 
two  parts  of  methyl  salicylate  are  heated  to  100° — 120°  with  one 
part  of  caustic  potash  and  three  or  four  parts  of  methyl  iodide, 
the  product  distilled  in  order  to  remove*  methyl  alcohol  and 
methyl,  iodide,  and  the  residue  then  extracted  with  caustic  soda 
and  precipitated  with  hydrochloric  acid.  Any  adhering  salicylic 
acid  is  removed  by  boiling  with  an  excess  of  milk  of  lime, 
insoluble  basic  calcium  salicylate  being  precipitated,  while 
calcium  methylsalicylate  remains  in  solution,  and  is  then 
decomposed  by  hydrochloric  acid.5 

Methylsalicylic  acid  crystallizes  from  hot  water  in  large, 
monoclinic  tablets,  and  from  alcohol  in  prisms,  which  melt  at 
98'5°  and  decompose  above  200°  into  carbon  dioxide  and  anisol. 

1  Jahns,  Arch.  Pharm.  [3]  xii.  212. 

2  Ann.  Chem.  Pharm.  xlviii.  83  ;  liii.  327. 

3  de  Vrij,  Pharm.  Journ.  Trans.  [3]  ii.  503  ;  Kohler,  Ber.  Deutsch.  Chem.  Ges. 
"\.  246.  4  Broughton,  Pharm.  Journ.  Trans.  [3]  ii.  281. 

6  Grabe,  Ann.  Chem.  Pharm.  cxxxix.  137. 


£06  AROMATIC  COMPOUNDS. 

On  heating  with  concentrated  hydrochloric  acid,  it  is  resolved 
into  salicylic  acid  and  methyl  chloride;  hydriodic  acid  has  a 
similar  action. 

The  sodium  salt  of  the  acid  is  formed,  together  with  a  little 
of  the  methyl  ether  and  sodium  salicylate,  when  winter-green 
oil  is  heated  with  sodium  : 

C6H4.ONa        C6H4.OH        C6H4.OCH3        C6H4.OH 

+    1  =1  +1 

C02.CH3  CO2.CH3        C02.CH3  C02Na. 

Two  molecules  of  the  sodium  compound  then  react  in  a 
similar  manner : 

C6H4.ONa        C02.CH3          C6H4.OCH3        C02Na 

+     1  +1 

02.CH3          C6H4.ONa        CO2Na  C6H4.OCH3. 


ETHEREAL  SALTS   OF  SALICYLIC  ACID. 

Melting    Boiling 
point.       point. 

2  Ethyl  salicylate,  C6H4(OH)C02.C2H5,           liquid  223° 

3  Propyl  salicylate,  C6H4(OH)C02.C3H7,         liquid  239° 

4  Amyl  salicylate,  C6H4(OH)CO2.C5Hn,          liquid  .  270° 

5  Ethylene  salicylate,  (C6H4(OH)C02)2C2H4,  needles     83° 

6  Propenyl  salicylate,  C6H4(OH)C02C3H5(OH)2,  liquid  —  — 


SALICYLIC   ETHERS. 

Melting-point. 

7  Ethysalicylic  acid,  C6H4(OC2H5)CO2H,  gradually  )       19<4o 

solidifying  oil j 

8  Isopropylsalicylic  acid,  C6H4(OC3H7)CO2H,  liquid  . 

9  Benzylsalicylic  acid,  C6H4(OC7H7)C02H,  small  tablets      75° 

10  Ethylenesalicylic  acid,  C6H4(OC6H4.CO2H)2,  long  )  151o_1520 

needles J 

1  Ann.  Chem.  Pharm.  cxlii.  327. 

2  Baly,  ibid.   Ixx.   269 ;   Schreiner,   ibid,  cxcvii.   17  ;   Gottig,    Ber.  Deutsch. 
Chem.  Ges.  ix.  1473.  3  Cahours,  Jahresb.  Chem.  1874,  333. 

4  Drion,  Ann.  Chem.  Pharm.  xcii.  313.       5  Gilmer,  ibid,  cxxvii.  377. 

6  Gottig,  Ber.  Deutsch.  Chem.  Ges.  x.  1817. 

7  Kraut,  Ann.  Chem.  Pharm.  cl.  1  ;  Gottig,  Ber.  Deutsch.  Chem.  Ges.  ix.  1474. 

8  Kraut.  9  Perkin,  Journ.  Chem.  Soc.  xxi.  125. 
10  Weddige,  Journ.  Prakt.  Chem.  [2]  xxi.  128. 


ETHYL  METHYLSALICYLATE.  307 


ETHEREAL  SALTS  OF  SALICYLIC  ETHERS. 

Boiling-point. 

1  Ethyl  methylsalicylate,  C6H4(OCH3)C02.C2H5,    .         260° 

2  Methyl  ethylsalicylate,  C6H4(OC2H5)CO2.CH3,    .    256°— 257° 

3  Ethyl  ethylsalicylate,  C6H4(OC2H5)C02.C2H5,      .     258°— 259° 

4  Methyl  isopropylsalicylate,  C6H4(OC3H7)C02.CH3,        250° 

5  Methyl  benzylsalicylate,C6H4(OC7H7)C02.CH3,  above  320° 

Melting-point. 

6  Ethyl  ethylenesalicylate,  C2H4(OC6H4<C02C2H5)2, )  96°_97o 

thick  plates j 


Phenyl  salicylate,  C6H4(OH)C02.C6H5.  Seifert7  obtained  this 
compound  by  heating  salicylic  acid  and  phenol  with  phosphorus 
oxychloride  : 

2C6H4(OH)C02H  +  2C6H5.OH  +  POC13  = 

2C6H4(OH)C02.C6H5  +  3HC1  +  HP03. 

A  better  yield  is  obtained  by  employing  the  sodium  salts ;  this 
ethereal  salt,  known  as  salol,  is  manufactured  by  heating  the 
product  of  the  action  of  carbon  dioxide  on  sodium  phenate  with 
phosphorus  pentachloride  or  oxychloride  : 

C6H4(OH)C02Na  +  C6H6.ONa  +  PC15= 

C6H4(OH)C02.C6H5  +  2NaCl  +  POC13. 

2C6H4(OH)C02Na+  2C6H5.ONa+POCl3  - 

2C6H4(OH)C02.C6H5  +  SNaCl  +  NaP03. 

Salol  crystallizes  in  rhombic  prisms,  which  are  odourless  and 
melt  at  42° — 42*5° ;  the  dilute  alcoholic  solution,  however,  has 
a  smell  resembling  that  of  winter-green  oil.  It  is  employed  in 
medicine  as  a  substitute  for  salicylic  acid,  because,  as  it  is  not 
decomposed  until  it  reaches  the  duodenum,  it  does  not  attack 
the  stomach  like  the  former :  when  applied  externally  it  has  no 
corrosive  action,  and,  on  account  of  its  lower  melting-point,  it 
can  be  more  conveniently  used  for  dressings,  &c.,  than  salicylic 
acid. 

1  Grabe  ;  Schreiner  ;  loc.  cif.  2  Schreiner  ;  loc.  cit. 

3  Gbttig  ;  Schreiner  ;  Zoc.  cit.  4  Kraut  ;  loc.  cit. 

5  Perkin  ;  loc.  cit.  6  Weddige  ;  loc.  cit. 
7  Journ.  Prakt.  Chem.  [2]  xxxi.  462. 


308  AROMATIC  COMPOUNDS. 

Phenyl  methylsalicylate,  C6H4(OCH3)C02.C6H5,  was  prepared  by 
Seifert  in  a  similar  manner  ;  it  crystallizes  in  six-sided  prisms, 
melting  at  59°. 

Acetylsalicylic  acid,  C6H4(O.CO.CH3)CO2H,  is  formed  by  the 
action  of  acetyl  chloride  on  salicylic  acid  or  its  sodium  salt,  and 
crystallizes  from  hot  water  in  fine  needles,  melting  at  118°  — 
118°'5.  Its  aqueous  solution  gives  a  violet  colouration  with 
ferric  chloride  ;  when  the  acid  is  heated  with  ammonia,  ammo- 
nium salicylate  is  formed,  but  no  salicylamide  (Kraut). 

/°\ 

Salicyl    chloraldide,    C6H4/          ^>CH.CC13,  is  formed   when 

>COo 

salicylic  acid  is  heated  to  130°  —  150°  for  a  long  time  with  an 
excess  of  chloral.  It  is  insoluble  in  water,  slightly  soluble  in 
alcohol  and  ether,  and  crystallizes  from  the  latter  in  prisms, 
melting  at  124°—  1250.1 

Disalicylic  acid,  (C6H4.C02H)20.  This  compound,  which  is 
also  called  salicylic  anhydride,  or  sal  icylo  salicylic  acid,  was  ob- 
tained b}r  Gerhardt  by  the  action  of  phosphorus  oxychloride  on 
sodium  salicylate.2 

It  is  also  formed  when  acetylsalicylic  acid  is  heated,  or  when 
salicylic  acid  is  heated  for  a  long  time  to  130°  —  140°  with  acetyl 
chloride.3  It  is  an  amorphous  mass,  which  dissolves  in  the 
alkaline  carbonates  and  is  reprecipitated  by  acids.  It  gives  no 
colouration  with  ferric  chloride  ;  aqueous  ammonia  converts  it 
into  salicylamide  and  ammonium  salicylate,  while  potassium 
salicylate  is  formed  by  the  action  of  caustic  potash. 

Salicylide,  C7H4O2,  is  formed  by  heating  salicylic  acid  with 
phosphorus  oxychloride  : 


=  c6H4<        +  H2o. 


It  crystallizes  from  absolute  alcohol  in  spherical  aggregates  of 
lustrous  plates,  which  melt  at  195°  —  200°;  it  gives  no  colour- 
ation with  ferric  chloride,  and  is  converted  into  salicylic  acid  by 
the  action  of  caustic  potash.4 

Tetrasalicylide,  C.28H1809,  is  formed  at  the  same  time  as  the 
preceding  compound,  and  is  a  resinous  mass  insoluble  in 
alcohol. 

1  Wallach,  Ann.  Chem.  Pharm.  cxcvii.  41.  2  Ibid.  Ixxxvii.  159. 

8  Kraut,  ibid.  cl.  13.  4  Schiff,  ibid,  clxiii.  220. 


SALICYLHYDROXYACETIC  ACID.  309 

Salicylhydroxyacetic  acid,  C6H4(OCH2CO2H)CO2H,  is  obtained 
by  oxidizing  ortho-aldehydophenoxyacetic  acid  (p.  289)  with 
potassium  permanganate.  It  crystallizes  from  hot  water  in 
white  needles,  melting  at  186° — 187°.  It  forms  readily  soluble 
salts  which  crystallize  well.1 

2175  The  Action  of  Phosphorus  Pentachloride  upon  Salicylic 
Acid.  As  already  mentioned,  Chiozza  found,  in  1852,  that  when 
salicylic  acid  is  treated  with  phosphorus  pentachloride  and 
the  product  distilled,  the  distillate  yields  orthochlorobenzoic 
acid  when  treated  with  water  (p.  217).  Gerhardt  repeated  this 
experiment,  and  found  that  the  liquid  before  distillation  is 
salicyl  chloride,  C7H5O2C1,  as  it  is  converted  by  water  into  sali- 
cylic acid,  and  by  alcohol  into  an  ethereal  salt  of  this ;  he  also 
obtained  it  together  with  methyl  alcohol  by  treating  winter-green 
oil  with  phosphorus  pentachloride.2  Drion  made  the  further 
observations  that  only  a  trace  of  phosphorus  oxychloride  is 
formed  in  this  reaction,  and  that  a  portion  of  the  product  is 
converted  into  chlorobenzoyl  chloride  by  distillation.3 

Couper,  however,  obtained  different  results.  He  acted  upon 
one  molecule  of  methyl  salicylate  with  two  molecules  of  phos- 
phorus chloride,  and  distilled  the  resulting  liquid ;  the  excess  of 
the  chloride  came  over  first,  followed  by  a  liquid  distilling  between 
285° — 295°,  to  which  he  gave  the  name  of  salicyl  trichlorophos- 
phate,  explaining  its  formation  by  the  following  equation : 

C8H803  f  PC15  =  HC1  +  CH3C1  +  C7H4C13P03. 

This  compound,  which  he  also  obtained  from  salicylic  acid,  is 
decomposed  by  water  into  hydrochloric  acid,  phosphoric  acid 
and  salicylic  acid  : 

C7H4C13P03  +  4H20  =  3HC1  +  H3P04  +  C7H603. 

When  he  submitted  it  to  rapid  distillation,  a  considerable 
quantity  of  hydrochloric  acid  was  evolved,  and  the  distillate 
consisted  of  a  liquid  boiling  above  300°,  which  deposited  large 
crystals  of  salicyl  monochlorophosphate,  C7H4C1P04,  when  pre- 
served in  a  sealed  tube ;  this  substance,  like  the  trichlorophos- 
phate,  is  converted  into  phosphosalicylic  acid,  C7H7PO6,  in  moist 
air.  He  therefore  considered  that  the  existence  of  salicyl 

1  Rossing,  Ber.  Deutsch.  Chem.  Ges.  xvii.  2988. 
3  Ann.  Chem.  Pharm.  Ixxxix.  363. 
8  Ibid.  xcii.  312. 

251 


310  AROMATIC  COMPOUNDS. 

chloride,  no  analyses  of  which  had  been  published,  was  very 
doubtful.1 

Drion  replied  to  this,  that  although  the  latter  compound  had 
not  been  obtained  in  a  state  of  purity,  its  existence  was  proved 
by  the  fact  that  ethers  of  salicylic  acid  are  formed  by  the  action 
of  alcohol  upon  it.2 

Kolbe  and  Lautemann  came  to  the  same  conclusion.  Accord- 
ing to  them,  a  mixture  of  chlorobenzoyl  chloride,  salicyl  chloride 
and  chlorosalicyl  trichloride  is  obtained  by  distilling  salicylic 
acid  with  phosphorus  pentachloride.3  Kekule",  who  investigated 
this  reaction  at  about  the  same  period,  found  that  when  the 
product  is  heated  to  180° — 200°  to  remove  phosphorus  chloride 
and  oxychloride,  a  liquid  remained  which  yielded  salicylic  acid  and 
traces  of  chlorobenzoic  acid  when  decomposed  by  water.  It  also 
contained  3  per  cent,  of  phosphorus,  and  considerably  more  chlorine 
than  corresponds  with  the  composition  of  salicyl  chloride  ;  on  dis- 
tillation he  obtained  considerable  quantities  of  phosphorus 
oxychloride  and  chlorobenzoyl  chloride,  but  not  Couper's  com- 
pound.4 

It  therefore  became  the  generally  accepted  view,  that  the 
following  compounds  are  formed  by  the  action  of  phosphorus 
pentachloride  on  salicylic  acid  : 

Salicyl  chloride.  Chlorobenzoyl  chloride.       Chlorobenzenyl  trichloride. 

/OH  /Cl  /Cl 

C6H4<  C6H4<(  C6H4<( 

\COC1  XJOC1  \CClr 

The  salicyl  chloride  could  not  be  obtained  pure  because  it 
decomposed  on  distillation,  and  could  not  therefore  be  freed 
from  chlorobenzoyl  chloride  and  phosphorus  oxychloride ; 
according  to  Miquel,  it  adheres  most  obstinately  to  the 
latter.5 

The  solution  of  the  problem  was  found  by  Anschiitz,  who,  by 
bringing  together  equal  molecules  of  salicylic  acid  and  phos- 
phorus pentachloride,  obtained  an  evolution  of  hydrochloric  acid 
and  a  yellow  liquid,  which  distilled  under  a  pressure  of  11  mm. 
as  a  colourless,  refractive  liquid,  only  a  small  quantity  of  residue 
being  left.  This  has  the  composition  of  Couper's  salicyl  tri- 

1  Ann.  Chem.  Pharm.  cix.  369.  2  Ibid.  cix.  373. 

3  Ibid.  cxv.  183.  4  Ibid,  cxvii.  148. 

5  Ann.  Chim.  Phys.  [5]  xi.  304. 


ORTHOCHLOROCARBONYLPHENYL  METAPHOSPHATE.  311 

chlorophosphate  and  is  orthocarbonylphenylphosphoryl  chloride, 
formed  according  to  the  following  equations  : 

/OH  /OH 

C6H4  <  +  PC15  =  C6H4<  +  POC13  +  H20. 

\CO.OH  \COC1 

The  phosphorus  oxychloride  then  acts  upon  the  salicyl  chloride 
just  as  it  does  upon  phenol  : 

/OH  /O.POC12 

C6H4<          +  POC13  =  C6H4<  4  HC1. 

\COC1  \COC12 

The  pure  chloride  distils  at  285°  —  295°  under  the  ordinary 
pressure.  If  it  be  submitted  to  slow  distillation,  a  mixture  of 
phosphorus  oxychloride,  orthochlorobenzoyl  chloride  and  ortho- 
chlorotribenzenyl  chloride  is  obtained,  boiling  at  270°  —  290°.  If 
the  distillation  be  now  continued  under  diminished  pressure, 
Couper's  salicyl  monochlorophosphate,  or  orthochlorocarbonyl- 
phcnyl  metaphosphate  passes  over;  it  is  formed,  together  with 
orthochlorobenzoyl  chloride,  according  to  the  following  equation  : 

O.POCL  /Cl  /OP09 


2C6H4  =C6H4  +  CflH  POC13. 

\COC1  \COC1  \COC1 

It  boils  at  187°  under  a  pressure  of  11  mm.,  and  solidifies  on 
cooling  to  crystals,  which  melt  at  30°. 

The  chloride  is  decomposed  by  a  small  quantity  of  water  into 
hydrochloric  acid,  phosphoric  acid  and  salicylic  acid  ;  in  moist 
air,  on  the  other  hand,  or  on  distillation  with  anhydrous  oxalic 
acid,  it  is  converted  into  orthochlorocarbonylphenyl  meta- 
phosphate : 

OPOC12  /OP0 


It  dissolves,  however,  in  a  large  quantity  of  cold  water,  with 
formation  of  orthocarboxylphenylphosphoric  acid,  C6H4(CO.OH) 
OPO(OH)2,  which  on  evaporation  in  a  vacuum  over  soda  lime 
gives  a  crystalline  mass,  which  melts  at  147°  and  is  readily 
soluble  in  water. 

If  the  chloride  be  heated  to  165°—  170°  with  phosphorus 
pentachloride,  benzenyltrichlorophosphoryl  chloride,  Cg 


312  AROMATIC  COMPOUNDS. 

CC13,  is  formed ;  it  is  a  powerfully  refractive  liquid,  which  boils 
at  178° — 179°  under  a  pressure  of  11 — 12  mm.,  and  is  not  con- 
verted by  water  into  hydroxybenzenyl  trichloride,  as  might  have 
been  expected,  but  into  phosphosalicylic  acid. 

When  it  is  heated  with  phosphorus  chloride  to  180°,  ortho- 
chlorobenzenyl  trichloride  is  formed  : l 

/OPOC12  ,01 

'C«H<cci3    +PC1-c<ccl3+2^- 

2176  Salicylamide,  C6H4(OH)CO.NH2,  is  obtained  by  the 
action  of  concentrated  ammonia  on  methyl  salicylate ; 2  it  cry- 
stallizes from  ether  in  lustrous,  yellow  plates,  melting  at  1420,3 
and  sublimes  when  carefully  heated.  As  a  phenol  it  forms 
metallic  salts ;  its  ethers  are  formed  when  ammonia  is  allowed  to 
act  upon  the  ethers  of  salicylic  acid. 

Benzoylsalicylamide,  C6H5(O.CO.C6H5)NH2,  is  formed  when 
salicylamide  is  heated  to  180°  with  benzoyl  chloride,  or  fused 
with  benzamide.4  It  is  slightly  soluble  in  alcohol,  but  almost 
insoluble  in  ether,  and  crystallizes  in  needles  melting  at  200°. 

Disalicylamide,  (C6H4(OH)CO)2NH,  is  prepared  by  heating 
salicylic  acid  in  a  current  of  hydrochloric  acid.  It  crystallizes 
in  yellowish  white  needles,  which  resemble  asbestos  in  appearance, 
and  melt  at  197° — 199°  with  partial  decomposition;  it  is  in- 
soluble in  water,  but  readily  dissolves  in  alcohol  and  alkalis.  The 
alcoholic  solution  is  coloured  red  by  ferric  chloride.5 

Salicylanilide,  C6H4(OH)CO.NH(C6H5),  is  obtained  by  gently 
warming  aniline  with  salicylic  acid  and  then  gradually  adding 
phosphorus  trichloride  to  the  cooled  mass.  It  crystallizes  from 
dilute  alcohol  in  small  prisms,  melting  at  184° — 135°;  ferric 
chloride  colours  the  solution  violet.6 

Salicyluric  acid,  C6H4(OH)CO.NH.CH2.C02H.  When  salicylic 
acid  is  administered  internally,  it  appears  in  the  urine  partly  in 
an  unaltered  state  and  partly  as  salicyluric  acid.  This  is  slightly 
soluble  in  water,  readily  in  alcohol,  and  crystallizes  in  fine 
needles,  which  melt  at  160°  and  give  a  violet  colouration  with 
feme  chloride.  On  heating  with  concentrated  hydrochloric  acid, 

1  Anschiitz,  Ann.  Chem.  Pharm.  ccxxviii.  308,  and  private  communication. 

2  Limpricht,  ibid,  xcviii.  258. 

3  Grimaux,  Bull.  Soc.  Chim.  xiii.  25. 

4  Chiozzaand  Gerhardt,  Jahresb.  Chem.  1856,  502. 
6  Schulerud,  Journ.  PraU.  Chem.  [2]  xxii.  298. 

6  Kupferberg,  ibid.  [2]  xvi.  442  ;  Wanstrat,  Ber.  Deulsch.  Chem.  Gcs.  vi.  336, 


CHLOROSALICYLIC  ACID.  313 

it  decomposes  into  salicylic  acid  and  amido-acetic  acid.  Its 
barium  salt  forms  prisms,  which  are  only  slightly  soluble  in 
water.1 

SaUcylnitril,  C6H4(OH)CN,  is  formed  by  heating  the  amide 
with  phosphorus  pentoxide,  and  is  a  colourless,  crystalline 
substance,  which  melts  at  195°,  and  on  boiling  with  dilute 
caustic  potash  is  converted  into  salicylic  acid.2 

Polysalicylnitril,  (C7H5ON)X.  Limpricht  obtained  this  com- 
pound by  heating  salicylamide  to  270°,  and  looked  upon  it  as  an 
imide  of  the  dibasic  salicylic  acid.3  It  is  a  yellow,  crystalline 
powder,  which  melts  at  280° — 285°  (Grimaux),  and  is  only 
converted  into  salicylic  acid  by  fusion  with  caustic  potash.  On 
heating  with  phosphorus  pentachloride,  orthochlorobenzonitril 
is  formed.4 

Benzoylsalicylnitril,  C6H4(OCO.C6H6)CN,  was  prepared  by 
Limpricht  by  heating  benzosalicylamide,  and  called  by  him 
benzoylsalicylimide.5  Henry  obtained  it  by  heating  the  poly- 
nitril  with  benzoyl  chloride.  It.  crystallizes  from  hot  alcohol  in 
small,  brittle,  lustrous  plates,  melting  at  148°— 149°.  The  hot 
alcoholic  solution  is  coloured  red  by  ferric  chloride. 


SUBSTITUTION  PRODUCTS  OF  SALICYLIC 

ACID. 

2177  Chlorosalicylic  acid,  C6H3C1(OH)C02H  (5  :  2  : 1),  is  formed 
by  passing  chlorine  into  a  solution  of  salicylic  acid  in  carbon 
disulphide,6  as  well  as  by  the  action  of  nitrous  acid  upon 
/3-chloramidobenzoic  acid.7  It  may  also  be  obtained  by  replacing 
the  amido-group  of  the  corresponding  amid osalicy lie  acid  by 
chlorine,8  and  by  heating  parachlorophenol  with  tetrachloro- 
methane  and  alcoholic  potash.9  It  dissolves  in  1100  parts  of 
water  at  20°,  and  in  80  parts  at  100°,  and  crystallizes  in  small 

1  Bertagrrini,  Ann.  Chem.  Pharm.  xcvii.  249. 

2  Grimaux,  Bull.  Soc.  Chim.  xiii.  26. 

3  Ann.  Chem.  Pharm.  xcviii.  261. 

4  Henry,  Ber.Deutsch.  Chem.  Ges.  ii.  491. 
8  Ann.  Chem.  Pharm.  xcix.  250. 

6  Hiibner  and  Brenkeu,  Ber.  Deutwh.  Chem.  Ges.  vi.  174. 

7  Hiibner  and  "Weiss,  ibid.  vi.  175. 

8  Schmitt,  Jahresb.   Chem.   1864,  385  ;  Beilstein,  Ber.  Deutsch.   Chem.   Ges. 
viii.  816. 

9  Hasse,  ibid.  x.  2190. 


314  AROMATIC  COMPOUNDS. 

needles,  melting  at  172°.    The  aqueous  solution  is  coloured  violet 
by  ferric  chloride. 

Dichlorosalicylic  acid,  C6H2C1?(OH)CO2H(3  :  5  :  2  : 1),  may  be 
prepared  by  heating  salicylic  acid  with  antimony  pentachloride,1 
as  well  as  by  the  action  of  chlorine  on  a  solution  of  salicylic 
acid  in  glacial  acetic  acid.2  It  is  also  slightly  soluble  in  boiling 
water,  and  crystallizes  from  dilute  alcohol  in  small  prisms,  which 
melt  at  214°,  and  are  coloured  dark  violet  by  ferric  chloride.  Con- 
centrated nitric  acid  converts  it  into  the  same  dichloronitrophenol 
as  is  formed  by  the  nitration  of  a-dichlorophenol.3 

a-Br&mosalicylic  acid,  C6H3Br(OH)CO2H(3  : 2  •.  1),  has  been 
obtained  from  the  corresponding  amidobromobenzoic  acid.4  It 
crystallizes  in  small,  soluble  needles,  melting  at  219° — 220°,  and 
gives  a  dark  reddish  blue  colouration  with  ferric  chloride. 

ft-Bromosalicylic    acid    (5:2:1)    is    formed    by    the    direct 
bromination  of  salicylic  acid,5  and  also  by  treating  /3-bromamido- 
benzoic  acid  with  nitrous  acid   (Hiibner  and  Heinzerling).     It 
crystallizes  from  hot  water  in  long  needles,  melting  at  164°— 
165° ;  ferric  chloride  colours  it  violet. 

Three  dibromosalicylic  acids  are  also  known.6 

lodosalicylic  acid,  C6H3I(OH)CO2H(5  : 2  : 1),  has  been  prepared 
from  the  corresponding  amido-salicylic  acid  by  means  of  the 
diazo-reaction.7  It  is  almost  insoluble  in  cold  water,  and  crystal- 
lizes from  alcohol  in  needles,  which  melt  at  196°,  and  decompose 
into  iodophenol  and  carbon  dioxide  when  they  are  rapidly  heated. 
The  same  acid  had  previously  been  obtained  by  Lautemann  by 
treating  salicylic  acid  with  iodine  and  caustic  potash  solution,8 
while  Liechti 9  and  Demole,10  by  the  action  of  iodine  and  iodic 
acid  on  salicylic  acid,  prepared  an  iodosalicylic  acid  which  is 
slightly  soluble  in  cold,  somewhat  more  readily  in  hot  water,  and 
crystallizes  in  needles,  melting  at  183°. 

Two  isomeric  acids  are  therefore  produced  by  the  direct  action 
of  iodine  on  salicylic  acid,11  and  probably  in  varying  proportions. 
The  following  compounds  are  also  formed  in  this  reaction  : 


1  Lossner,  Joum.  Prdkt.  Cham.  [2]  xiii.  429. 

2  Smith,  Bcr.  Deutsch.  Chem.  Ges.  xi.  1225. 

3  Smith  and  Knerr,  Amer.  Chem.  Journ.  viii.  95. 

4  Hiibuer  and  Heinzerling,  Zcitschr.  Chem.  1871,  709. 

5  Henry,  Ber.  Deutsch.  Chem.  Ges.  ii.  275  ;  Hiibner  and  Heinzerling. 

6  Rollwage,  ibid.  x.  1707;  Smith,  ibid.  1706  ;  Hiibner,  ibid.  1706. 

7  Goldberg,  Journ.  PraJct.   Chem.  [2]  xix.  368  ;  Hiibner,  Ber.   Deutsch.  Chem. 
Ges.  xii.  1347.  8  Ann.    Chem.  Pharm.  cxx.  302. 

9  Ibid.  Suppl.  vii.  136.  10  Ber.  Deutsch.  Chem.  Ges.  vii.  1437. 

11  Fischer,  Ann.  Chem.  Pharm.  clxxx.  346. 


NITROSALICYLIC  ACIDS.  315 

Di-iodosalicylic  acid,  C6H2I2(OH)CO2H,  is  best  obtained  by 
the  action  of  iodine  and  mercuric  oxide  upon  an  alcoholic 
solution  of  salicylic  acid.1  It  is  slightly  soluble  in  cold,  more 
readily  in  hot  water  and  alcohol,  crystallizes  in  needles,  melting 
at  220° — 280°,  and,  like  moniodosalicylic  acid,  is  coloured  violet 
by  ferric  chloride. 

Tri-iodosalicylic  acid,  C6HI3(OH)CO2H,  is  insoluble  in  water, 
and  crystallizes  from  alcohol  in  yellow  needles. 

2178  Nitrosalicylic  acids.  In  the  year  1806,  Fourcroy  and 
Vauquelin  obtained  a  volatile,  crystalline  acid,  which  they 
thought  was  benzoic  acid,  by  treating  indigo  blue  with  dilute 
nitric  acid.  Chevreul  recognized  the  individuality  of  this  sub- 
stance, which  was  called  indigotic  acid,  and  it  was  then  carefully 
examined  by  Buff,2  and  correctly  analysed  by  Dumas.3  Marchand4 
confirmed  the  results  obtained  by  Dumas,  and  found,  as  also 
did  Gerhardt,5  that  indigotic  acid  is  identical  with  nitrosalicylic 
acid.  Piria,  by  the  action  of  nitric  acid  on  salicin,  obtained 
helicin  and  anilotic  acid,  which,  according  to  Major,  is  identical 
with  nitrosalicylic  acid,  although  Piria  himself  was  convinced 
that  the  two  acids  were  different  substances.6  In  spite  of  this, 
it  was  generally  assumed  that  only  one  nitrosalicylic  acid  existed, 
until  Hiibner  found  that  two  are  formed  by  the  nitration  of 
salicylic  acid.7  One  of  these  is  identical  with  anilotic  acid,  while 
indigotic  acid  proves  to  be  a  mixture  of  both.8  These  acids  are 
also  formed  when  the  vapour  of  nitric  acid  is  passed  into  methyl 
salicylate.9 

a-Nitrosalicylic  acid,  (CO2H  :  OH  :NO2  =  1 :  2  :  5),  may  be 
obtained,  in  addition  to  the  methods  given  above,  by  heating 
paranitrophenol  with  tetrachlorom ethane  and  alcoholic  potash 
to  1000,10  by  boiling  e-nitro-amidobenzoic  acid  with  caustic  potash 
solution,11  and  by  passing  nitrogen  tetroxide  into  a  cold  aqueous 
solution  of  salicylic  acid  (Hiibner).  In  order  to  prepare  it,  100 
parts  of  salicylic  acid  are  dissolved  in  800  parts  of  glacial  acetic 
acid,  50  parts  of  pure  nitric  acid,  of  sp.  gr.  of  1'5,  being  then 

1  Weselsky,  Ann.  Chem.  Pharm.  clxxiv.  103. 

2  Schweigg,  Journ.  Chem.  Phys.  li.  38  ;  liv.  163. 
8  Ann.  Chim.  Phys.  [3]  ii.  224. 

4  Journ.  Prakt.  Chem.  xxvi.  385. 

5  Ann.  Chem.  Pharm.  xlv.  19. 

6  Ibid,  xcvii.  253. 

7  Ibid.  cxcv.  1. 

8  Masino  and  Schiff,  ibid,  cxcviii.  256. 

9  Smith  and  Kiierr  ;  Amer.  Chem.  Journ.  viii.  99. 

10  Hasse,  Ber.  Deutsch.  Chem.  Ges.  x.  2188. 

11  Griess,  ibid.  xi.  1730. 


316  AROMATIC  COMPOUNDS. 

gradually  added  in  the  cold ;  the  solution  is  then  diluted  with 
two  or  three  volumes  of  water,  and  the  acid,  which  separates 
out  after  some  time,  purified  by  repeated  crystallization  from  hot 
water.  The  barium  salt  of  the  yS-acid  may  be  prepared  from 
the  mother-liquor;  it  is  only  slightly  soluble  in  water. 

a-Nitrosalicylic  acid  crystallizes  in  long  needles,  which  melt 
at  228°  and  dissolve  in  1475  parts  of  water  at  15°;  it  is  more 
easily  soluble  in  alcohol  or  hot  water.  Its  solution  is  coloured 
blood-red  by  ferric  chloride.  Boiling  nitric  acid  converts  it  into 
picric  acid,  and  when  its  diethyl  ether  is  heated  to  130°  with 
alcoholic  ammonia,  the  amide  of  e-amidonitrobenzoic  acid  is 
obtained.  On  heating  with  lime  it  decomposes  into  carbon 
dioxide  and  paranitrophenol. 

Normal  barium  a-nitrosalicylate,  (C7H4N05)2Ba  H-  fflgO,1  is 
obtained  by  heating  the  acid  with  water  and  barium  carbonate  ; 
it  is  readily  soluble  in  water,  and  crystallizes  in  compact,  yel- 
low needles  which  form  fascicular  aggregates.  The  basic  salt, 
C7H3NO6Ba  4-  2H2O,  is  formed  by  boiling  the  acid  with  baryta 
water,  and  crystallizes  in  citron-yellow  plates,  which  have  a  satin 
lustre  and  are  only  slightly  soluble  in  water. 

ft-Nitrosalicylic  acid,  or  Anilotic  acid,  (C02H  :  OH :  N02  = 
1:2: 3),  is  formed  in  largest  quantity  by  the  action  of  the  most 
concentrated  nitric  acid  upon  salicylic  acid  at  a  low  temperature,2 
and  has  also  been  obtained  by  heating  orthonitrophenol  with 
tetrachloromethane  and  alcoholic  potash  (Hasse).  In  order  to 
prepare  it,  10  grms.  of  salicylic  acid  are  gradually  brought  into 
a  mixture  of  10  grms.  of  concentrated  nitric  acid  with  10 — 12 
grms.  of  glacial  acetic  acid  at  a  temperature  of  about  6°.  The 
solution  is  then  poured  into  250  ccm.  of  water  and  the 
precipitated  acids  separated  by  means  of  their  barium  salts. 

/3-Nitrosalicylic  acid  dissolves  in  770  parts  of  water  at  15 "5°, 
readily  in  alcohol  and  ether,  and  crystallizes  in  long  needles, 
which  contain  a  molecule  of  water,  and  melt  at  125°.  The 
anhydrous  acid  melts  at  144°;  its  solution  is  coloured  blood-red 
by  ferric  chloride ;  on  heating  with  lime  it  decomposes  into 
carbon  dioxide  and  orthonitrophenol,  while  the  amide  of  f-amido- 
nitrobenzoic  acid  is  formed  by  the  action  of  alcoholic  ammonia 
on  its  diethyl  ether. 

Normal  barium  fB-nitrosalicylate,  (C7H4N05)2Ba,  crystallizes 
in  golden  yellow  plates  or  compact,  refractive  needles,  which  are 

1  Ann.  Chem.  Pkarm.  ccr.  344. 

2  Schaumann,  Ber.  Deutsch.  Chem.  Ges.  xii.  1346. 


DINITROSALICYLIC  ACID.  317 

only  very  slightly  soluble  in  cold,  more  readily  in  hot  water. 
Ammonia  added  to  the  solution  produces  a  deep-red  colouration 
and  then  a  precipitate  of  the  basic  salt,  2C7H3NO5Ba  +  3H2O,  in 
thick,  blood-red  needles. 

Dinitrosalicylic  acid,  C6H2(NO.2)2(OH)C02H.  The  methyl 
ether  of  this  compound  was  obtained  by  Cahours  by  dropping 
winter-green  oil  into  a  mixture  of  fuming  nitric  and  sulphuric 
acids.1  It  crystallizes  in  yellow  scales,  which  melt  at  127° — 128° 
(Salkowski),  and  are  easily  saponified  by  caustic  potash.  Sten- 
house  then  prepared  dinitrosalicylic  acid  by  the  action  of  nitric 
acid  on  the  aqueous  extracts  of  Populus  nigra  and  P.  balsam- 
ifera,  which  contain  populin.2  It  is  also  formed  by  the 
further  nitration  of  both  the  mononitrosalicylic  acids,  their 
constitution  being  thus  shown.  It  is  best  prepared  by  bringing 
10  grms.  of  salicylic  acid  into  70  grms.  of  the  most  concentrated 
nitric  acid  at  0°,  and  pouring  the  clear  solution  into  300  ccm.  of 
water;  after  standing  for  24 — 36  hours  the  separated  acid  is 
filtered  off,  pressed,  converted  into  the  barium  salt  by  boiling 
with  water  and  barium  carbonate,  and  re-precipitated  by  hydro- 
chloric acid.3 

Dinitrosalicylic  acid  is  readily  soluble  in  cold,  very  readily  in 
hot  water,  and  crystallizes  therefrom  in  thick,  lustrous  plates,  or, 
on  rapid  cooling,  in  fine  needles  containing  one  molecule  of 
water.  Its  solution  is  coloured  dark-red  by  ferric  chloride ;  on 
heating  with  water  to  200°  it  decomposes  into  carbon  dioxide 
and  ordinary  dinitrophenol. 

Potassium  -dinitrosalicylate.  When  caustic  potash  is  added  in 
excess  to  the  aqueous  solution  of  the  acid,  the  salt  C6H2(N02)2 
(OK)CO2K -f- H2O  is  formed;  it  crystallizes  in  long,  dark-red 
needles,  which  detonate  violently  when  heated.  Dilute  hydro- 
chloric acid  or  nitric  acid  added  to  its  solution  precipitates  the 
salt  C6H2(NO2)2(OH)CO2K,  which  crystallizes  from  boiling 
water  in  compact,  short,  dark  yellow  needles. 

Barium  dinitrosalicylate,  C6H2(NO2)2OBaC02  +  3H20,  forms 
compact,  yellow  needles,  which  are  only  slightly  soluble  in  cold 
water. 

2179  a-Amidosalicylic  acid,  C6H3(NH2)(OH)C02H,  was  ob- 
tained by  Beilstein  by  reducing  nitrosalicylic  acid  with  tin  and 
hydrochloric  acid  ; 4  it  is  better,  however,  to  employ  acetic  acid 
(Hiibner).  It  crystallizes  in  needles  which  have  a  satin  lustre, 

1  Ann.  Chem.  Pharm.  Ixix.  232.  2  Ibid.  Ixxviii.  1. 

3  Hiibner,  ibid.  cxcv.  45.  4  Ann.  Chem.  Pharm.  cxxx.  243. 


318  AROMATIC  COMPOUNDS. 

and  are  insoluble  in  alcohol  and  cold  water,  but  slightly  soluble 
in  hot  water  ;  the  solution  soon  decomposes  in  the  air,  a  brown, 
amorphous  substance  being  precipitated.  Ferric  chloride  pro- 
duces a  cherry-red  colouration,  followed  by  a  brownish  black 
precipitate. 

Amidosalicylic  acid  forms  salts  both  with  bases  and  acids  ;  it 
decomposes  on  heating  into  carbon  dioxide  and  paramidophenol.1 

CO 


TrimetJiylamidosalicylic  acid,  C6H3(OH)<;      ^>0.       This  com- 

\N(CH3)3 

pound,  which  may  also  be  called  hydroxybenzobetaine,  is  formed 
by  the  action  of  methyl  iodide  and  caustic  potash  on  amidosalicylic 
acid,  and  crystallizes  from  water  in  large,  snow-white  needles, 
often  an  inch  in  length,  which  contain  four  molecules  of  water, 
have  a  very  bitter  taste  and  are  coloured  reddish  violet  by  ferric 
chloride.  It  combines  with  the  mineral  acids  to  form  salts 
which  crystallize  well. 

Methyl  dimethylamidosalicylate,  C6H3(OH)N(CH3)2C02CH3,  is 
prepared  by  heating  the  preceding  compound,  after  previously 
removing  its  water  of  crystallization.  It  forms  rhombic  prisms, 
and  is  decomposed  on  boiling  with  hydrochloric  acid  into  methyl 
alcohol  and  dimethylamidosalicylic  acid,  which  crystallizes  in 
small,  almost  insoluble  needles.2 

(3-  Amidosalicylic  acid  is  not  known  in  the  free  state;  its 
hydrochloride  crystallizes  in  needles  which  readily  decompose 
(Hubner). 

Nitro-amidosalicylic  acid,  C6H2(NO2)NH2(OH)C02H,  is  formed 
by  the  partial  reduction  of  dinitrosalicylic  acid  ;  it  forms  crystals, 
melting  at  220°  ;  a-nitrosalicylic  is  obtained  3  when  the  amido- 
group  is  replaced  by  hydrogen. 

Diamidosalicylic  acid,  C6H2(NH2)(OH)CO2H,  was  prepared  by 
Saytzew  by  the  action  of  hydriodic  acid  on  the  methyl  ether 
of  dinitrosalicylic  acid.4  It  is  very  slightly  soluble  in  cold, 
more  readily  in  hot  water,  and  crystallizes  in  small  needles.  It 
combines  with  acids  to  form  salts  which  crystallize  well  ;  ferric 
chloride  produces  a  brownish  red  colouration,  followed  by  a  black 
precipitate. 

Sulphosalicylic  acid,  C6H3(S03H)(OH)C02H,  was  obtained  by 
Mendius  by  the  action  of  sulphur  trioxide  on  salicylic  acid,5  and 


1  Schmitt,  Jahresber.  1864,  423. 

2  Griess,  Ber.  Dcutsch.  Ctwm.  Ges.  xii.  2307.  3  Babcock,  ibid.  xii.  1345. 
*  Ann.  Chcm.  Pharm.  cxxxiii.  321.                            5  Ibid.  ciii. 


DIAZOSALICYLIC  ACID.  319 

may  also  be  prepared  by  heating  salicylic  acid  with  sulphuric 
acid.1  It  crystallizes  in  long,  thin,  very  soluble  needles,  which 
melt  at  120°,  and  are  coloured  an  intense  reddish  violet  by  ferric 
chloride.  Its  salts  crystallize  well  ;  on  fusion  with  caustic  potash, 
no  dihydroxybenzene  is  formed,  the  product  consisting  entirely 
of  phenol  and  salicylic  acid. 

Salieylsulphuric  acid,  C6H4(SO4H)C02H.  The  potassium  salt 
may  be  obtained  by  heating  salicylic  acid  with  caustic  potash 
and  potassium  disulphate  ;  it  crystallizes  in  colourless,  pointed 
prisms  and  is  readily  soluble  in  water,  but  insoluble  in  absolute 
alcohol.  It  gives  no  colouration  with  ferric  chloride  and  is 
decomposed  by  dilute  acids,  including  even  acetic  acid,  into 
potassium  sulphate  and  salicylic  acid.2 

,!$=$ 

Diazosalicylic  acid,  C6H3(OH)<;  |  ,  is  formed  by  passing 


;  | 

\co.o 


nitrogen  trioxide  into  an  alcoholic  solution  of  the  hydrochloride 
of  amidosalicylic  acid.  It  crystallizes  in  fine  needles  and  combines 
with  acids  to  form  salts  which  crystallize  well  ;  3  iodosalicylic 
acid  is  formed  on  heating  with  hydriodic  acid. 

Azobenzenesalicylic  acid,  C6H5.N2.C6H3(OH)C02H,  is  obtained 
by  the  action  of  diazobenzene  nitrate  on  an  alkaline  solution  of 
salicylic  acid  ;  it  crystallizes  in  orange  -red  needles,  which  are 
insoluble  in  water,  but  dissolve  readily  in  alcohol.  Sulphuric 
acid  converts  it  into  a  sulphonic  acid,  which  is  probably  identical 
with  the  following  compound.4 

Salicylparazobenzenesulphonic  acid,  C6H4(SO3H)N2.C6H3(OH) 
C02H,  is  formed  by  bringing  salicylic  acid  into  a  solution  of 
paradiazobenzenesulphonic  acid  in  caustic  potash.  It  crystallizes 
in  golden-yellow  needles,  which  are  only  slightly  soluble  in 
hot  water  ;  barium  chloride  produces  a  yellow  precipitate  of 
(C13H9N2S06)2Ba,  which  is  converted  on  boiling  into  irregular, 
six-sided,  lustrous  plates.5 

1  Remsen,  Ann.  Chem.  Pharm.  clxxix.  107. 

2  Baumann,  Ber.  Dcutsch.  Chem.  Ges.  xi.  1914. 

3  Schmitt,    Jahresber.    Chem.    1864,  384  ;  Schmidt   and  Mittenzwey,    Journ. 
Prakt.  Chem.  [2]  xviii.  193  ;  Goldberg,  ibid.  x'ix.  362. 

4  Stebbins,  Ber.  Deutsch.  Chem.  Ges.  xiii.  716. 
6  Griess,  ibid.  xi.  2196. 


320  AROMATIC  COMPOUNDS. 


METAHYDROXYBENZOIC  ACID. 

2180  Gerland  obtained  this  isomeride  of  salicylic  acid  by  the 
action  of  nitrous  acid  on  a  hot  solution  of  ordinary  amidobenzoic 
acid,  and  gave  it  the  name  of  oxybenzoic  acid,1  by  which  it  is 
still  generally  designated.  It  is  also  formed  by  fusing  sulpho- 
benzoic  acid,2  metachlorobenzoic  acid,3  or  metachlorocresol 4  with 
caustic  potash. 

In  order  to  prepare  it,  2  parts  of  potassium  sulphobenzoate 
are  fused  with  5  parts  of  caustic  potash  and  a  little  water,  the 
melt  acidified  with  sulphuric  acid  and  the  whole  extracted  with 
ether. 

The  metahydroxybenzoic  acid  is  left  on  evaporation  in  thick, 
white  crusts  which  are  purified  by  re-crystallization  from  hot 
water.  Any  adhering  benzoic  acid  is  finally  removed  by 
washing  with  carbon  disulphide  (Barth). 

Metahydroxybenzoic  acid  crystallizes  in  small  prisms  or 
needles,  melting  at  200°,  which  usually  form  warty  aggregates. 
It  dissolves  at  0°  in  265,  and  at  18°  in  108'2  parts  of  water,  has 
a  sweet  taste,  is  not  coloured  by  feme  chloride  and  can  be 
distilled  without  undergoing  decomposition.  It  differs  from  its 
isomerides  in  being  reduced  by  sodium  amalgam  in  an  acid 
solution  to  metahydroxybenzyl  alcohol,  and  in  blackening  at  300° 
without  a  trace  of  phenol  being  formed ;  decomposition,  accom- 
panied by  the  formation  of  small  quantities  of  the  latter,  only 
occurs  at  higher  temperatures.5 

The  Metahydroxybenzoates.  The  salts  of  the  alkali  metals  are 
readily  soluble  and  do  not  crystallize  well ;  they  are  very  stable 
and  only  decompose  at  a  high  temperature,  very  little  phenol 
and  no  isomeric  acid  being  formed.  The  basic  salts  do  not 
combine  with  carbon  dioxide  at  a  high  temperature  (Kupferberg)  ; 
when  the  acid  is  fused  with  an  excess  of  sodium  carbonate, 
decomposition  sets  in  above  300°,  the  greater  portion  of  the 
acid  being  completely  burnt,  and  only  a  small  quantity  of  phenol 
being  therefore  formed.6  If  two  molecules  of  the  acid  are  heated 

1  Ann.  Chem.  Pharm.  Ixxxvi.  143  ;  xci.  189  ;  Fischer,  ibid,  cxxvii.  138. 

2  Barth,  ibid,  cxlviii.  30.  3  Dembey,  ibid,  cxlviii.  222. 
4  Barth,  ibid.  cliv.  361. 

6  Klepl,  Journ.  Prakt,  Chem.  [2]  xxv.  464  ;  xxvii.  159. 
6  Barth  and  Schreder,  Ber.  Deutsch.  Chem.  Ges.  xii.  1254. 


THE  METAHYDROXYBENZOATES.  321 

to  350°  with  three  molecules  of  caustic  baryta,  no  change  takes 
place,  but  if  seven  molecules  of  the  latter  be  employed,  a 
complete  decomposition  into  carbon  dioxide  and  phenol  occurs 
(Klepl). 

Ammonium  metahydroxybenzoate,  C6H4(OH)C02NH4,  crystal- 
lizes in  needles  which  form  fascicular  aggregates. 

Calcium  metahydroxybenzoate,  (C6H4.OH.CO2)2Ca  +  3H2O, 
forms  readily  soluble  crystals. 

Barium  metahydroxybenzoate,  (C6H4.OH.C02)0Ba,  is  an  amor- 
phous, gummy  mass ;  it  has  been  found  impossible  to  prepare  a 
basic  salt. 

Copper  metahydroxybenzoate,  (C6H.i.O'H..CO^)2C\i +H20,  crystal- 
lizes from  hot  water  in  greenish  needles. 

Thallium  metahydroxybenzoate,  C6H4(OH)CO2T1,  is  prepared  by 
neutralizing  a  hot  solution  of  the  acid  with  thallium  carbonate  ; 
it  crystallizes  on  cooling  in  lustrous,  colourless  prisms.  When  a 
solution  of  the  hydroxide  is  neutralized  with  the  acid  and  an 
equal  quantity  of  the  hydroxide  added  to  the  neutral  solution, 
the  basic  salt,  C6H4(OT1)CO2T1,  crystallizes  on  evaporation  in 
yellowish  prisms ;  it  is  more  readily  soluble  than  the  normal 
salt  and  has  an  alkaline  reaction  (Kupferberg). 

The  methylamine  salt  decomposes  into  its  constituents  when 
heated,  and  the  aniline  salt  behaves  in  a  similar  manner,  a  little 
hydroxybenzanilide  being  also  formed,  while  tetra-ethylammonium 
metahydroxybenzoate  splits  up  into  tri-ethylamine  and  ethyl 
metahydroxybenzoate. 

Ethyl  metahydroxybenzoate,  C6H4(OH)CO2.C2H5,  is  formed  by 
the  action  of  hydrochloric  acid  gas  on  an  alcoholic  solution  of  the 
acid,1  or  by  heating  the  normal  potassium  salt  with  ethyl  iodide.2 
It  crystallizes  from  ether  in  tablets,  melts  at  72°,  boils  at  282°, 
and  is  converted  by  caustic  soda  into  a  crystalline  mass 
of  C6H4(ONa)C02.C2H5,  which  is  readily  soluble  in  water 
and  alcohol. 

Metamethoxybenzoic  acid,  C6H4(OCH3)CO2H,  is  obtained  by 
heating  metahydroxybenzoic  acid  with  the  calculated  quantity  of 
caustic  potash  and  methyl  iodide,  and  decomposing  the  ethereal 
salt  thus  formed  with  a  solution  of  caustic  potash  in  wood-spirit 
(Grabe  and  Schultzen).  It  is  also  formed  by  the  oxidation  of 
metacresyl  methyl  ether  with  potassium  permanganate,3  and  by 

1  Grabe  and  Schultzen,  Ann.   Chem.  Pharm.  cxlii.  351. 

2  Heiutz,  ibid,  cliii.  337. 

3  Oppenheim  and  Pfaff,  Ber.  Deutsch.  Chem.  Ges.  viii.  887. 


322  AROMATIC  COMPOUNDS. 

the  action  of  carbon  dioxide  on  a  mixture  of  metabromophenyl 
methyl  ether  and  sodium.1  It  crystallizes  from  hot  water  in 
long  needles,  which  melt  at  106° — 107°,  and  sublime  without 
decomposition. 

Meta-ethoxylenzoic  acid,  C6H4(OC2H5)C02H,  was  prepared  by 
Heintz  from  the  ethyl  ether ;  it  is  also  formed  by  the  decom- 
position of  the  sulphate  of  metadiazobenzoic  acid  with  alcohol 2 
It  crystallizes  in  small  needles,  melting  at  137°,  which  are 
scarcely  soluble  in  cold,  slightly  in  hot  water,  but  readily  in 
alcohol,  and  sublime  undecomposed. 

Ethyl  meta-ethoxylenzoate,  C6H4(OC2H5)C02.C2H5,  is  obtained 
by  heating  metahydroxybenzoic  acid  with  two  molecules  of 
caustic  potash  and  ethyl  iodide ;  it  is  a  liquid,  boiling  at  263°. 

Meta-acetoxybenzoic  acid,  C6H4(OCO.CH3)C02H,  is  produced 
by  the  action  of  acetyl  chloride  on  the  acid  (Heintz) ;  it  forms 
granular  crystals  melting  at  127°,  and  gives  amorphous  salts. 

2181  Metahydroxybenzoic  acid  behaves  towards  phosphorus 
pentachloride  in  a  very  similar  manner  to  salicylic  acid. 

Metacarbonylphenylphosphoryl  chloride,  C6H4(OPOC12)COC1,  is 
a  colourless  liquid,  which  boils  at  168° — 170°  under  a  pressure 
of  11 — 12  mm.  A  yield  of  57'5  per  cent,  of  the  theoretical 
quantity  is  obtained,  and  the  unattacked  acid  may  be  extracted 
from  the  residue  in  the  retort  by  boiling  water  or  alkalis. 

Metacarboxyorthophosphoric  acid,  C6H4(CO2H)PO(OH)2,  is 
formed  when  the  chloride  is  treated  with  water,  a  considerable 
evolution  of  heat  taking  place,  but  no  metahydroxybenzoic  acid 
being  reformed.  It  crystallizes  in  fine,  white  scales,  which  melt 
at  200° — 201°,  and  are  only  decomposed  by  water  at  a  tem- 
perature of  150° — 160°,  phosphoric  and  metahydroxybenzoic 
acids  being  formed. 

When  the  chloride  is  submitted  to  slow  distillation,  a  portion 
passes  over  unchanged,  together  with  phosphorus  oxychloride, 
no  metachlorobenzoyl  chloride,  C6H4C1(COC1),  or  metachloro- 
benzenyl  trichloride,  C6H4C1(CC13),  being  produced,  and  a  black 
syrupy  residue  is  left,  which  yields  metahydroxybenzoic  acid  on 
boiling  with  water  or  alkalis,  and  therefore  probably  contains  the 
compounds  (C6H4(COC1)0)2POC1  and  (C6H4(COC1)0)3PO. 

Metabenzenyltrichlorophosphoryl  chloride,  C6H4(OPOC12)CC13, 
is  obtained  in  a  similar  manner  to  the  corresponding  salicylic  acid 
derivative.  It  boils  at  178°  under  a  pressure  of  11  mm.,  and  is 

1  Korner,  Jahresber.  Chem.  1867,  414. 

2  Griess,  Zeitschr.  Chem.  1866,  1. 


IODOMETAHYDROXYBENZOIC  ACID.  323 

converted  by  water  into  metacarboxyphenylphosphoric  acid, 
while  on  heating  with  phosphorus  pentachloride  to  180°,  a 
portion  is  converted  into  metachlorobenzenyl  trichloride.1 

Metahydroxylenzamide,  C6H4(OH)CO.NH2,  is  formed  when 
diazobenzamide  nitrate  is  boiled  with  water 2  as  well  as  by  the 
action  of  ammonia  on  ethyl  metahydroxybenzoate.  It  crystallizes 
from  water  in  thin  plates,  which  have  a  bitter  taste  and  melt 
at  167°. 

MetaJiydroxylenzanilid.c,  C6H4(OH)CO.NH(C6H5),  is  obtained 
in  the  same  way  as  salicylanilide  ;  it  crystallizes  from  dilute 
alcohol  in  needles,  melting  at  154° — 155°,  and  combines  with 
alkalis  to  form  salts  which  crystallize  well.  It  is  not  attacked 
by  boiling  alkalis,  but  is  decomposed  by  them  on  fusion 
(Kupferberg). 

Metahydroxylenzuric  acid,  C6H4(OH)CO.NH.CH2.CO2H,  occurs 
in  the  urine  of  the  dog  after  metahydroxybenzoic  acid  has  been 
administered  ;  it  crystallizes  in  needles.3 

Metahydroxylenzonitril,  C6H4(OH)CN,  is  formed  by  boiling 
diazobenzonitril  sulphate  with  water4  and  by  heating  meta- 
hydroxybenzoic acid  in  a  current  of  ammonia,  first  to  220° — 230° 
and  then  to  300° — 320° ;  the  isomeric  compounds  are  decomposed 
by  this  treatment  into  phenol  and  carbon  dioxide,  but  yield  no 
nitril.5  Metahydroxybenzonitril  crystallizes  from  hot  water  in 
small  plates  and  from  alcohol  in  small,  rhombic  prisms ;  it  has 
an  intensely  sweet  and  at  the  same  time  sharp  taste,  melts  at 
82°,  and  decomposes  on  heating  with  hydrochloric  acid  into 
ammonia  and  metahydroxybenzoic  acid. 


SUBSTITUTION  PRODUCTS  OF  METAHYDROXY- 
BENZOIC ACID. 

2182  Iodometahydroxy'benzoicacid)CQH.3l(01I)CO.fi.  Weselsky 
obtained  this  substance  by  the  action  of  iodine  and  mercuric 
oxide  on  an  alcoholic  solution  of  metahydroxybenzoic  acid.  It  cry- 
stallizes in  needles,  which  are  only  slightly  soluble  in  cold  water. 

Nitrometahydroxybenzoic  «aWs,C6H3(NO2)(OH)CO2H.  Gerland 
found  that  the  direct  nitration  of  metahydroxybenzoic  acid  yields 

1  Anschiitz,  private  communication. 

2  Griess,  Zeitschr.  Chem.  1866,  1. 

3  Baumann  arid  Heiter,  Hoppe-Seyler's  Zeitschrift,  i.  260. 

4  Griess,  Ber.  Deutsch.  Chem.  Ges.  viii.  859. 

5  Smith,  Journ.  Prakt.  Chem.  [2]  xvi.  218. 


324  AROMATIC  COMPOUNDS. 

a  nitrohydroxybenzoic  acid,  -which  forms  yellow,  rhombic  crystals, 
and  has  a  repulsive,  bitter  taste ;  it  must  be  identical  with 
one  of  those  described  below,  since  metahydroxybenzoic  acid  can 
only  yield  four  mononitro-derivatives.  The  first  three  were 
prepared  by  Griess  by  boiling  the  corresponding  nitro-amido- 
benzoic  acids  with  caustic  potash.1 

a-Nitrometahydroxylenzoic  acid,  (CO2H  :  OH  :  NO2  =  1:3:6), 
is  readily  soluble  in  water,  and  crystallizes  in  thick,  honey-yellow 
prisms  or  in  needles  containing  one  molecule  of  water,  which  is 
given  off  at  a  few  degrees  above  100°.  It  melts  at  169°,  has  a 
slightly  acid  taste,  and  is  coloured  a  faint  reddish  brown  by  ferric 
chloride.  The  barium  salt,  C7H3NO5Ba  +  6H2O,  forms  yellowish 
red  prisms,  which  are  readily  soluble  in  water. 

(S-Nitrometahydroxylenzoic  acid  (1 :  3  : 4),  is  slightly  soluble  in 
hot  water,  and  crystallizes  in  long,  yellow,  four-  or  six-sided 
plates,  melting  at  230°.  The  barium  salt,  C7H3NO5Ba  +  H2O,  is 
almost  insoluble  and  crystallizes  in  yellowish  red  plates. 

ry-Nitrometahydroxybenzoic  acid  (1:3:  2),is  less  soluble  in  water 
than  the  a-acid,  has  an  intensely  sweet  taste,  and  crystallizes 
with  one  molecule  of  water  in  long,  four-sided  plates  or  large 
tablets,  which  melt  at  178°  and  give  a  faint  reddish  brown 
colouration  with  ferric  chloride.  The  barium  salt,  2C7H3NO5Ba 
+  3H2O,  also  has  a  very  sweet  taste,  and  forms  tolerably  soluble 
reddish  brown  plates. 

ri-Nitrometahydroxylenzoic  acid  (1:3:  5),  was  prepared  by 
Grube  from  the  corresponding  nitro-amidobenzoic  acid,2  and  is  a 
yellowish  brown,  crystalline  precipitate.  Its  salts  crystallize  badly. 

Trinitrometahydroxy'benzoic  acid,  C6H(NO2)3(OH)CO2H,  is 
formed  by  heating  diazo-amidobenzoic  acid  with  ordinary  strong 
nitric  acid,3  and  by  the  action  of  fuming  nitric  acid  on  metamido- 
benzoic  acid.4  It  crystallizes  in  large,  almost  colourless,  rhombic 
prisms,  which  have  a  vitreous  lustre,  and  are  best  obtained 
from  solution  in  concentrated  nitric  acid  ;  it  is  readily  dissolved 
by  water,  alcohol,  and  ether,  forming  intensely  yellow  solutions, 
which  dye  animal  fabrics  in  the  same  way  as  picric  acid.  It 
melts  when  heated  and  then  explodes. 

The  barium  salt,  C7HN3O9Ba  +  3H2O,  is  tolerably  soluble  in 
water,  but  insoluble  in  alcohol,  and  crystallizes  in  thick,  light 
yellow  needles,  which  are  very  explosive. 

1  Bcr.  Deutsch.  Chem.  Ges.  xi.  1729.  2  Ibid.  x.  1704. 

8  Griess,  Ann.  Chem.  Pharm.  cxvii.  28. 
4  Beilstein  and  Geitner,  ibid,  cxxxix.  11 


THIOMETAHYDROXYBENZOIC  ACID.  325 

When  metahydroxybenzoic  acid  is  heated  with  sulphuric  acid, 
three  compounds  isomeric  with  alizarin,  C14H8O4,  are  formed.1  If 
the  product  be  .boiled  with  strong  nitric  acid,  a  trinitrometahy- 
droxybenzoic  acid  is  produced  among  other  products,  which  is 
readily  soluble  in  water,  and  crystallizes  in  tablets  or  prisms  con- 
taining one  molecule  of  water,  which  is  lost  at  100°.  It  melts  at  105° 
and  then  commences  to  sublime ;  when  rapidly  heated  it  detonates. 
The  barium  salt,  C7HN309Ba  +  2H20,  is  readily  soluble  in  water, 
and  crystallizes  in  yellow  needles,  which  explode  at  29 9°.2 

Thiometahydroxybenzoic  acid,  C6H4(SH)CO2H,  is  formed  by  the 
action  of  tin  and  hydrochloric  acid  on  sulphobenzoyl  chloride, 
C6H4(SO2C1)COC1.  It  is  tolerably  soluble  in  water,  more  readily 
in  alcohol,  and  sublimes  very  easily  in  small  plates,  melting  at 
146°— 147°. 

Dithiometahydroxybenzoic  acid,  S2(C6H4.C02H)2,  is  obtained  by 
exposing  the  monothio-compound  to  the  air  in  the  moist  state, 
or  more  rapidly  by  adding  bromine  water  to  its  aqueous  solution.3 
Griess  prepared  it  by  decomposing  diazobenzoic  acid  aurichloride 
with  sulphuretted  hydrogen  : 4 

3C1N2C6H4.C02H  +  2H2S  = 

S.C6H4.C09H 

J  +  C6H5.C02H43HC1  +  3N9. 
SC6H4.C02H 

It  crystallizes  in  microscopic  needles,  which  are  scarcely  soluble 
in  water,  more  readily  in  alcohol,  and  melt  at  242° — 244°. 

Sulplwmetahydroxybenzoic  acid,  C6H3(S03H)(OH)C02H,  is 
formed  by  the  action  of  sulphur  trioxide  on  metahydroxybenzoic 
acid  ;  it  crystallizes  in  green,  deliquescent  needles,  melting  at 
208°,  is  almost  insoluble  in  ether  and  is  coloured  wine-red  by 
ferric  chloride.5 

Isosulplwmetahydroxylenzoic  acid  is  obtained  by  dissolving  the 
sulphate  of  diazobenzoic  acid  in  warm  sulphuric  acid ;  it  crystal- 
lizes in  plates,  which  are  readily  soluble  in  water  and  alcohol.  It 
is  decomposed  by  strong  nitric  acid  into  trinitrometahydroxy- 
benzoic  acid  and  sulphuric  acid.6 

1  Schunck  and  Romer,  Ber.  Deutsch.  Chem.  Ges.  xi.  1167. 

2  Schardinger,  ibid:  viii.  1490. 

3  Hiibner  and  Upmann,  Zeitschr.   Chem.  1870,   294  ;  Frerichs,  Ber.  Deutsch. 
Chem.  Ges.  vii.  793. 

4  Journ.  Prakt.  Chem.  [2]  i.  102. 

5  Earth,  Ann.  Chem.  Pharm.  cxlviii.  38  ;  Senhofer,  ibid.  clii.  102. 

6  Griess,  Jahresber.  Chem.  1864,  351. 

252 


AROMATIC  COMPOUNDS. 


DisulpJiometahydroxy'benzoic  acid,  C6H2(S03H)2(OH)C02H, 
seems  to  be  formed  when  metahydroxybenzonitril  is  heated  with 
fuming  sulphuric  acid ; l  its  barium  salt  is  obtained  by  boiling 
the  following  compound  with  baryta  water.2 

Trisulphometahydroxylenzoic  acid,  C6H(SO3H)3(OH)C02H,  is 
obtained  by  heating  metahydroxybenzoic  acid  to  250°  with  a  mix- 
ture of  fuming  sulphuric  acid  and  phosphorus  pentoxide.  The 
free  acid  is  a  honey-yellow  syrup ;  it  is  coloured  an  intense 
carmine-red  by  ferric  chloride,  and  on  fusion  with  caustic  potash 
undergoes  complete  oxidation. 

Metahydroxylcnzoylsulphuric  acid,  C6H4(S04H)C02H,  is  found 
in  the  urine  of  men  and  dogs  after  the  administration  of  meta- 
hydroxybenzoic acid  (Baumann  and  Heiter).  Its  potassium 
salt  is  obtained  in  a  similar  manner  to  that  of  salicylsulphuric 
acid  ;  it  forms  deliquescent  needles,  and  decomposes  on  boiling 
with  hydrochloric  acid  or  alcoholic  potash  into  metahydroxy- 
benzoic acid  and  sulphuric  acid.3 


PARAHYDROXYBENZOIC  ACID. 

2183  Fischer  obtained  this  acid  by  the  action  of  nitrous  acid 
on  an  aqueous  solution  of  paramidobenzoic  acid,4  and  Saytzew 
by  heating  anisic  acid  (methylparahydroxybenzoic  acid)  with 
hydriodic  acid.5  It  is  also  formed  when  para-compounds  such  as 
anisic  acid,6  paracresol,7  parasulphobenzoic  acid,8  &c.,  are  fused 
with  caustic  potash ;  it  may  be  obtained  by  the  same  method 
from  various  resins,  as  gum  benzoin,  dragon's  blood,  aloes  and 
acaroid  resin.9 

Kolbe  prepared  it  synthetically  by  adding  potassium  to  boiling 
phenol  and  at  the  same  time  passing  in  carbon  dioxide ;  para- 
hydroxybenzoic  acid  alone  is  formed,  while  if  the  temperature  be 
not  allowed  to  rise  above  130° — 150°,  salicylic  acid  is  obtained. 

Parahydroxybenzoic  acid  may  also  be  prepared  by  the  action 

1  Smith,  Joum.  Prakt.  Chem.  [2]  xvi.  229. 

2  Kretschy,  Ber.  Deutsch.  Chem.  Ges.  xi.  858. 
Baumann,  ibid.  xi.  1915. 

Ann.  Chem.  Pharm.  cxxvii.  129. 
Ibid,  cxxvii.  145. 

Earth,  Zeitschrift.  Chem.  1866,  650. 
Earth,  Ann.  Chem.  Pharm.  cliv.  359. 

8  Remsen,  ibid  clxxviii.  281. 

9  Earth  and  Hlasiwetz,  ibid,  cxxxiv.  274  ;  cxxxix.  78. 


PARAHYDROXYBENZOIC  ACID.  327 

of  carbon  dioxide  on  potassium  phenate  at  170° — 21 00;1  it  is 
formed  in  sma-11  quantities,  together  with  salicylic  acid,  when 
sodium  phenate  is  treated  in  a  similar  manner  at  a  lower 
temperature.2  The  fact  that  normal  potassium  salicylate  de- 
composes at  220°  into  carbon  dioxide,  phenol  and  basic  potassium 
parahydroxybenzoate,  has  been  already  mentioned.  Parahydroxy- 
benzoic  acid  is  further  obtained,  together  with  a  smaller  quantity 
of  salicylic  acid,3  by  heating  tetrachloromethane  to  100°  with 
phenol  and  alcoholic  soda.4 

It  is  formed  in  theoretical  amount  when  the  potassium  salt 
of  paracresylsulphuric  acid  is  oxidized  with  potassium  per- 
manganate in  alkaline  solution.5  Paracresol  is  also  converted 
into  parahydroxybenzoic  acid  in  passing  through  the  animal 
organism,  while  metacresol  is  found  in  the  urine  as  metacresyl- 
sulphuric  acid,  and  orthocresol  is  partly  converted  into  ortho- 
cresylsulphuric  acid  and  partly  into  hydrotoluquinone.6 

In  order  to  prepare  parahydroxybenzoic  acid,  a  mixture  of 
equal  molecules  of  caustic  potash  and  phenol  is  heated  in  a 
current  of  hydrogen,  the  temperature  being  finally  raised  to  180° ; 
carbon  dioxide  is  then  passed  in  until  the  theoretical  quantity  of 
phenol  has  distilled  over,  and  the  residue  is  then  dissolved  in  water 
and  decomposed  by  hydrochloric  acid.  The  parahydroxybenzoic 
acid  is  boiled  with  animal  charcoal  and  crystallized  from  hot 
water.  It  is  thus  obtained  in  small,  monoclinic  prisms,  while  it 
is  deposited  from  dilute  alcohol  in  larger  crystals,7  containing 
one  molecule  of  water,  which  is  lost  at  100°;  it  dissolves  in  580 
parts  of  water  at  0°,  and  in  126  parts  at  15°,  and  is  readily  soluble 
in  hot  water,  alcohol  and  ether,  but  only  slightly  in  chloroform, 
which  is  therefore  employed  to  free  it  from  salicylic  acid.  Its 
slight  solubility  in  carbon  disulphide  is  made  use  of  in  separating 
it  from  benzoic  acid.  It  melts  at  200°  and  when  rapidly  heated 
decomposes  partly  into  carbon  dioxide  and  phenol,  and  partly 
into  other  products,  which  will  be  described  below.  It  decom- 
poses completely  and  readily  into  phenol  and  carbon  dioxide  on 
heating  with  dilute  sulphuric  acid  in  a  sealed  tube.8  Its  aqueous 
solution  gives  an  amorphous,  yellow  precipitate  with  ferric 

1  Kolbe,  Joum.  PraJct.  Chem.  [2]  x.  100. 

2  Ost,  ibid.  [2]  xx.  208. 

3  Hasse,  Her.  Deutsch.  Chem.  Gfes.  ix.  2186. 

4  Reimer  and  Tiemann,  ibid.  ix.  1285. 

5  Heymann  and  Kbnigs,  ibid.  xix.  704. 

6  Baumann  and  Preusse,  ibid.  xix.  706. 

7  Hartmann,  Joum.  Prakt.  Chem.  [2]  xvi.  35. 

8  Klepl,  ibid.  [2]  xxv.  464. 


328  AROMATIC  COMPOUNDS. 

chloride.     Phosphorus  pentachloride  converts  it  into  parachloro- 
benzoyl  chloride. 

The  Parahydroxylenzoates.  The  normal  sodium  salt  decom- 
poses completely  at  240° — 250°  into  carbon  dioxide,  phenol  and 
the  basic  salt ;  when,  however,  it  is  heated  to  280° — 295°  in  a, 
current  of  carbon  dioxide,  salicylic  acid  is  obtained,  while  both 
hydroxyisophthalic  acid  and  hydroxytrimesic  acid  are  formed 
at  temperatures  above  340°  (Kupferberg).  When,  on  the  other 
hand,  the  acid  is  heated  with  eight  to  ten  parts  of  caustic  soda, 
a  partial  decomposition  into  phenol  and  carbon  dioxide  sets  in  at 
355°  (Barth  and  Schreder),  The  salts  of  methylamine  and 
aniline  decompose  at  a  higher  temperature  into  phenol,  carbon 
dioxide  and  the  base,  while  that  of  tetra-ethylammonium 
decomposes  on  distillation  into  tri-ethylamine  and  ethyl  para- 
hydroxybenzoate,  the  latter  of  which  is  then  partially  resolved 
into  carbon  dioxide  and  phenetol. 

Sodium  parahydroxylenzoate,  C6H4(OH/CO2Na  +  5H2O,  crys- 
tallizes from  concentrated  solutions  in  transparent  tablets,  which 
effloresce  in  the  air. 

Potassium  parahydroxybenzoate,  C6H4(OH)C02K  +  3H90,  is 
similar  to  the  sodium  salt,  but  is  stable  in  the  air. 

Ammonium  parahydroxylienzoate,  C6H4(OH)CO2NH4  -f  H20, 
crystallizes  in  long  prisms. 

Calcium parahydroxylenzoate,  (C7H5O3)2Ca  +  4H20,  forms  fine 
needtes  grouped  in  stellate  forms,  and  is  very  soluble. 

Barium  parahydroxylenzoate,  (C7H5O3)2Ba  +  H20,  crystallizes 
in  flat,  lustrous  needles  or  with  two  molecules  of  water  in 
pointed  rhombohedra ;  baryta  water  added  to  its  solution  pro- 
duces a  precipitate  of  the  basic  salt,  C7H4O3Ba,  as  a  sandy, 
crystalline  powder,  which  is  scarcely  soluble  in  cold  water. 

Lead  parahydroxylenzoate,  (C7H5O3)2Pb  -f  2H20,  is  a  very 
characteristic  salt,  and  is  obtained  by  neutralizing  the  boiling 
aqueous  solution  of  the  acid  with  lead  carbonate.  It  separates 
out  on  cooling  in  thin,  iridescent  plates  which  take  a  silver 
lustre  on  drying,  and  resemble  those  of  benzoic  acid. 

Copper  parahydroxybenzoate,  (C7H5O3)2Cu  +  6H20,  crystal- 
lizes in  small,  bluish  green  needles,  which  become  dull  and 
insoluble  on  boiling  with  water. 

Silver  parahydroxylenzoate,  C7H503Ag  +  2H20,  crystallizes 
from  hot  water  in  small,  lustrous  plates. 

Methyl  parahydroxylenzoate,  C6H4(OH)C02CH3,  is  formed  by 
heating  together  equal  molecules  of  parahydroxybenzoic  acid, 


ANISIC  ACID.  329 


caustic  potash  and  methyl  iodide ;  it  crystallizes  from  ether  in 
large  tablets,  melts  at  17°  and  boils  at  2830.1 

2 184  Paramethoxylenzoic  acid,  or  Anisic  acid,  C6H4(OCH3)C02H. 
Cahours  obtained  this  compound  in  1839  by  the  oxidation  of  oil  of 
anise-seed,  and  showed  at  the  same  time  that  it  is  formed  from  the 
"  camphor "  (anethol  or  allylphenol,  C6H4(OH)C3H5),  contained 
in  this  substance.2  Laurent,  in  1841,  prepared  from  tarragon  oil 
(from  Artemisia  dracunculus),  the  so-called  dragonic  acid  (acide 
draconique),  which,  according  to  Gerhardt,  is  identical  with  anisic 
acid.  This  view  was  subsequently  confirmed  by  Laurent,  who 
also  accurately  determined  its  composition.3 

At  about  the  same  time  Persoz  submitted  oil  of  anise -seed, 
fennel  oil,  and  star-anise  oil  (Jiuile  de  badiane,  from  Illicium 
anisatuni)  to  oxidation,  and  obtained  two  acids,  which  he  named 
umbellic  acid  (acide  ombellique)  and  badianic  acid  (acide 
ladianique)*  Hempel  showed,  however,  that  these  are  both 
anisic  acid,5  the  formation  of  which  might  have  been  expected, 
since  the  oils  employed  contain  anethol.6 

Anisic  acid  was  at  first  looked  upon  as  the  homologue  of 
salicylic  acid ;  Kolbe,  however,  considered  it  to  be  methoxy- 
benzoic  acid,  since  it  behaves  very  similarly  to  benzoic  acid,  and 
decomposes  into  anisol  (phenyl  methyl  ether)  and  carbon  dioxide 
when  distilled  with  caustic  baryta.7 

In  order  to  determine  from  which  of  the  hydroxybenzoic 
acids  it  is  derived,  Saytzew  heated  it  with  hydriodic  acid,  and 
found  that  the  product  consists  of  parahydroxybenzoic  acid.  It 
was  then  thought  probable  that  anisic  acid  and  winter-green  oil 
would  have  similar  constitutions,  but  Grabe  showed  that  the 
latter  is  the  methyl  ether  of  salicylic  acid,  while  Ladenburg 
proved  that  in  anisic  acid  the  methyl  group  replaces  the 
hydrogen  of  the  phenol  hydroxyl ;  by  heating  equal  molecules  of 
potassium  parahydroxybenzoate  and  caustic  potash  with  two 
molecules  of  methyl  iodide,  he  obtained  the  methyl  ether  of 
paramethoxybenzoic  acid  (anisic  acid)  and  prepared  the  free  acid 
by  saponifying  with  potash  and  decomposing  the  product  with 
hydrochloric  acid.8  Anisic  acid  may  also  be  obtained  by 
oxidizing  orthocresyl  methyl  ether  with  chromic  acid  solution.9 

1  Ladenburg  and  Fitz,  Ann.  Chem.  Pharm.  cxli.  247. 

2  Ibid.  xli.  66.  3  Ibid.  xliv.  313.  4  Ibid.  xliv.  311. 
8  Ibid.  lix.  104.              6  Cahours,  ibid.  xxxv.  312. 

7  Lehrb.  d.  Organ.  Chem.  ii.  135. 

8  Ann.  Chem.  Pharm.  cxli.  241. 

9  Korner,  Zeitschr.  Chem.  1868,  326. 


320  AROMATIC  COMPOUNDS. 

In  order  to  prepare  it,  1  part  of  oil  of  anise  seed  is  poured 
into  a  solution  of  5  parts  of  potassium  dichromate  in  10  parts 
of  sulphuric  acid  and  20  parts  of  water,  which  is  heated  to  50°. 
The  reaction  is  completed  in  a  few  minutes  and  the  solution  is 
then  allowed  to  cool,  the  anisic  acid  filtered  off  and  purified  by 
precipitation  with  hydrochloric  acid  from  solution  in  ammonia 
(Ladenburg  and  Fitz). 

It  crystallizes  in  long  monoclinic  prisms  or  needles,  melting 
at  184%  which  dissolve  in  2500  parts  of  water  at  18°.  It  is 
tolerably  soluble  in  boiling  water  and  very  readily  in  alcohol. 
On  heating  with  hydriodic  or  concentrated  hydrochloric  acid,  or 
on  fusion  with  potash,  it  is  converted  into  parahydroxybenzoic 
acid. 

Its  salts,  which  crystallize  well,  have  been  chiefly  investigated 
by  Engelhardt  and  by  Borella.1 

Melting-point.     Boiling-point. 

Methyl  paramethoxybenzoate,2 

C6H4(OCH3)C02.CH3,  scales     .        .       45°— 46°  255° 

Ethyl  paramethoxybenzoate,3 

C6H4(OCH3)C02.C2H5,  liquid  ,.        .  250°— 255C 

Ethyl  parahydroxybenzoate,4 

C6H4(OH)CO2.C2H5,  crystals     .        .  116°        297°— 298° 

Para-ethoxybenzoic  acid,5 

C6H4(OC2H5)C02H,  needles      .        .          195° 
Ethyl  para-ethoxybenzoate,6 

C6H4(OC2H5)C02.C2H5,  liquid   .  275° 

f 

Para-acetoxybenzoic  acid,  C6H4(OCO.CH3)CO2H,  is  formed 
when  parahydroxybenzoic  acid  is  heated  with  acetic  anhy- 
dride. It  is  slightly  soluble  in  water,  and  crystallizes  from 
chloroform  in  large  plates,  which  have  a  silver  lustre  and  melt 
at  185°  (Klepl). 

Phenyl  parahydroxybenzoate,  C6H4(OH)CO2.C6H5,  occurs  in  the 
products  which  are  formed  by  the  dry  distillation  of  the  acid.  It 
is  insoluble  in  water,  but  readily  soluble  in  alcohol  and  chloro- 
form, from  which  it  crystallizes  in  compact,  rhombic  tablets,  which 
melt  at  176°,  dissolve  readily  in  caustic  soda,  and  are  decom- 

1  Gaz.   Chim.  Ital.  xv.  304  ;  Ann.  Chem.  Pharm.  cviii.  240. 

2  Ladenburg  and  Fitz,  ibid.  cxli.  252. 

3  Cahours,  ibid.  Ivi.  310. 

4  Grabe,  ibid,  cxxxix.  146  ;  Hartmann,  Journ.  PraU.  Chem.  [2]  xvi.  50. 

5  Ladenburg  and  Fitz  ;  Fuchs,  Ber.  Deutsch.  Chem.  Ges.  ii.  624. 

6  Ladenburg  and  Fitz. 


METHYL  PARAMETHOXYBENZOATE.  331 

posed  by  it  even  in  the  cold  with  formation  of  phenol  and 
parahydroxybenzoic  acid  (Klepl). 

Paraphcnoxylenzoic  acid,  C6H4(OC6H5)CO2H,  is  obtained  by 
boiling  the  following  compound  with  alcoholic  potash,  or  by  heat- 
ing it  to  200°  with  concentrated  hydrochloric  acid.  It  is  readily 
soluble  in  alcohol  and  ether,  and  crystallizes  from  chloroform  in 
long  prisms  melting  at  159'5°.  When  heated  with  caustic  baryta 
it  decomposes  into  carbon  dioxide  and  diphenyl  ether. 

Phenyl  paraphcnoxylenzoate,  C6H4(OC6H5)C02.C6H5,  is  formed 
when  parahydroxybenzide,  which  is  described  below,  is  heated 
to  about  400°,  preferably  in  a  current  of  carbon  dioxide.  It 
crystallizes  from  dilute  alcohol  in  fatty  scales,  which  melt  at 
73°  —  78°,  and  sublime  at  a  higher  temperature,  forming  a  vapour 
which  smells  like  the  geranium. 

2185  Anhydrides  of  parahydroxybenzoic  acid.  When  para- 
hydroxybenzoic acid  is  submitted  to  dry  distillation,  only  half 
of  it  is  decomposed  into  carbon  dioxide  and  phenol,  which  distils 
over  accompanied  by  water,  and  phenyl  parahydroxybenzoate  ; 
as  the  distillation  is  continued,  the  boiling  acid  suddenly 
becomes  turbid,  and  a  milky  liquid  settles  in  the  retort,  until 
at  350°  the  residue  solidifies  to  a  white  amorphous  mass.1 

Parahydroxybcnzoylparahydroxyltenzoic  acid, 

XOCO.C6H4.OH 
C6H  4<f  .     In  order  to  prepare  this  compound,  the 

\C02H 

distillation  is  stopped  as  soon  as  the  acid  has  lost  about  15  per 
cent,  of  its  weight  and  before  any  turbidity  has  appeared.  The 
residue  is  boiled  with  chloroform  and  water,  and  the  compound 
then  extracted  with  dilute  alcohol  and  purified  by  re-crystal- 
lization. It  forms  short,  microscopic  needles,  which  melt  at 
261°  and  are  rapidly  converted  into  parahydroxybenzoic  acid  in 
alkaline  solution.  As  a  monobasic  acid  it  forms  a  barium  salt, 
(C14H905)9Ba,  which  crystallizes  in  long  plates  containing  water 
of  crystallization.  On  heating  with  acetic  anhydride,  the  mono- 
acetyl  compound,  C14H9(C2H3O)O5,  is  formed  ;  it  crystallizes  in 
small  plates,  melting  at  216*5°. 

Diparahydroxybenzoylparahydroxybenzoic  acid, 
OCO.C6H4O.CO.C6H4.OH 

,  is  contained  in  the  residue  ob- 


tained  in  the  preparation  of  the  preceding  compound,  and  also  in 
1  Klepl,  Journ.  Praki.  Chem.  [2]  xxv.  525  ;  xxviii.  193. 


332  AROMATIC  COMPOUNDS. 

the  amorphous  mass  formed  by  the  distillation  of  parahydroxy- 
benzoic  acid,  from  which  it  may  be  extracted  by  absolute  alcohol. 
It  is  a  white,  non-crystalline  powder,  which  is  slightly  soluble  in 
alcohol  and  ether,  but  insoluble  in  water  and  chloroform;  it 
melts  at  280°,  and  readily  dissolves  in  alkalis,  being  gradually 
converted  into  parahydroxybenzoic  acid,  while  it  is  not  altered 
by  boiling  water.  When  the  acid  is  suspended  in  a  small 
quantity  of  water  and  treated  with  sufficient  caustic  soda  to 
effect  solution,  the  compound  C21H13O7Na  is  precipitated  in 
needles  after  some  time.  The  acetyl  compound,  C21H13(C2H3O)O7, 
is  formed  by  heating  the  acid  with  acetic  acid  ;  it  crystallizes  in 
needles  melting  at  230°. 

Parahydroxylenzide,  (C7H4O2)n,  is  the  final  product  of  the 
action  of  heat  upon  parahydroxybenzoic  acid,  and  forms  a  white, 
amorphous  powder,  which  is  insoluble  in  the  ordinary  solvents, 
and  carbonizes  at  350°  without  previously  melting.  Boiling 
concentrated  caustic  potash  converts  it  into  parahydroxybenzoic 
acid ;  on  heating  with  concentrated  sulphuric  acid,  parahydroxy- 
benzoylsulphuric  acid  is  obtained,  while  parachlorobenzenyl 
trichloride  is  formed  by  the  action  of  phosphorus  chloride  at  300° 
(p.  196). 

Anisic  anhydride,  (C6H4(OCH3N/CO)2O,  is  obtained  by  the 
action  of  phosphorus  oxychloride  on  sodium  anisate.  It  crys- 
tallizes from  ether  in  small,  silky  needles,  which  melt  at  99° 
and  volatilize  at  a  higher  temperature  without  decomposition.1 

Methylparahydroxybenzoyl  chloride,  or  Anisyl  chloride,  C6H4 
(OCH3)COC1,  is  formed  by  the  action  of  phosphorus  penta- 
chloride  on  anisic  acid.2  It  forms  long  needles,  which  cannot  be 
volatilized.3 

Paracarbonylphenylphosplwryl  chloride,  C6H4(OPOC12)COC1> 
is  prepared  by  the  action  of  phosphorus  pentachloride  on  de- 
hydrated parahydroxybenzoic  acid,  the  reaction  being  more 
violent  than  in  the  case  of  salicylic  or  metahydroxybenzoic  acids. 
It  boils  at  176°  under  a  pressure  of  13 — 14  mm.,  and  is  a 
powerfully  refractive  liquid.  Water  converts  it  into  paracarbonyl- 
orthophosphoric  acid,  C6H4(C02H)PO(OH)2,  which  crystallizes  in 
fine,  white  plates,  melting  at  200° ;  it  is  only  decomposed  by 
water  at  150° — 160°,  parahydroxybenzoic  and  phosphoric  acids 
being  formed.  When  the  chloride  is  distilled  slowly  under  the 
ordinary  pressure,  it  passes  over  almost  unaltered,  only  a  small 

1  Pisani,  Ann.  Chem.  Pkarm.  cii.  284.  2  Cahours,  ibid.  Ixx.  47- 

3  Lessen,  ibid,  clxxv.  284. 


ANISIC  ANHYDRIDE.  333 

portion  decomposing  into  phosphorus  oxychloride  and  para- 
chlorobenzoyl  chloride. 

The  behaviour  of  this  chloride  towards  a  second  molecule  of 
phosphorus  pentachloride  is  of  considerable  interest,  since  it 
differs  from  that  of  its  isomerides  inasmuch  as  no  parabenzenyl- 
trichlorophosphoryl  chloride  is  formed,  but  the  compound 
decomposes  into  phosphorus  oxychloride  and  parachlorobenzoyl 
chloride,  the  latter  being  then  partially  converted  into  para- 
chlorobenzenyl  trichloride.  The  phenol-oxygen  is  therefore 
more  readily  replaced  by  chlorine  when  it  occupies  the  para- 
position  than  when  it  is  present  in  either  an  ortho-  or 
meta-disubstituted  compound.1 

Parahydroxylenzamide,  C6H4(OH)CO.NH2  +  H2O,  is  obtained 
by  heating  the  ethyl  ether  with  ammonia  under  pressure.  It 
crystallizes  from  hot  water  in  strongly  lustrous,  rhombic  needles, 
which  lose  their  water  of  crystallization  at  100°  and  then  melt 
at  162.° 

Anisamide,  C6H4(OCH3)CO.NH2,  was  prepared  by  Cahours 
from  the  chloride  by  the  action  of  ammonia ;  it  crystallizes  in 
prisms,  melts  at  137° — 138°,  sublimes  in  broad  plates  and  boils 
at  295°  (Henry). 

Parahydroxylenzanilide,  C6H4(OH)CO.NH(C6H5),  is  formed 
when  the  acid  is  heated  with  aniline  and  the  product  treated 
with  phosphorus  trichloride.  It  crystallizes  from  hot  water  in 
yellowish,  lustrous  plates,  melting  at  196° — 197°.  It  forms 
salts  of  potassium  and  sodium,  which  are  readily  soluble  and 
crystallize  well  (Kupferberg). 

Anisanilide,    C6H4(OCH3)CO.NH(C6H5),    was    obtained    by 

ssen  as  a  product  of  the  distillation  of  benzanishydroxamic 
acid  (p.  340).  It  is  slightly  soluble  in  cold  alcohol,  and 
crystallizes  in  rhombic  plates,  melting  at  168° — 169°. 

Parahydroxylenzuric  acid,  C6H4(OH)CO.NH.CH2.CO2H,  ap- 
pears, together  with  parahydroxybenzoylsulphuric  acid,  in  the 
urine  of  the  dog  after  the  administration  of  parahydroxybenzoic 
acid  ;  it  crystallizes  in  short  prisms,  which  are  tolerably  soluble 
in  water  (Baumann  and  Heiter). 

Anisuric  acid,  C6H4(OCH3)CO.NH.CH2.CO2H,  was  obtained 
by  Cahours  from  silver  amido-acetate  and  anisyl  chloride,2  and  is 
also  found  in  the  urine  after  anisic  acid  has  been  taken ; 3  it 

1  Anschiitz,  private  communication. 

2  Ann.  Chem:  Pharm.  cix.  32. 

3  Griibe  and  Schultzen,  ibid,  cxlii.  348. 


334  AROMATIC  COMPOUNDS. 

forms  foliaceous  crystals,  which  are  readily  soluble  in  hot 
water. 

Parahydroxylenzonitril,  C6H4(OH)CN,  is  formed  when  am- 
monium parahydroxybenzoate  mixed  with  phosphorus  pentoxide 
is  distilled  in  a  current  of  carbon  dioxide  (Hartmann),  and 
by  the  action  of  ammonia  on  parahydroxybenzide  mixed  with 
pumice-stone  and  heated  to  250°  (Klepl).  It  crystallizes  from 
hot  water  in  rhombic  tablets,  which  melt  at  113°,  and  have  a 
sweet  but  pungent  taste ;  it  forms  a  series  of  salts  in  which  the 
phenol-hydrogen  is  replaced  by  the  metal. 

Anisonitril,  C6H4(OCH3)CN.  Henry  obtained  this  substance 
by  distilling  the  amide  with  phosphorus  pentachloride.  It 
crystallizes  from  hot  water  in  small  needles,  and  from  ether  in 
long,  white,  lustrous  prisms,  has  a  penetrating,  characteristic 
rank  odour,  melts  at  56°— 57°,  and  boils  at  253° — 2540.1 


SUBSTITUTION  PRODUCTS  OF  PARAHYDROXY- 
BENZOIC    ACID. 

2186  ChloroparaJiydroxylenzoic  acid,  C6H3C1(OH)C02H, 
(3:4: 1),  is  formed  by  heating  parahydroxybenzoic  acid  with 
antimony  pentachloride,2  and  by  the  action  of  alcoholic  potash 
on  orthochlorophenol  at  125° — 136°.3  It  is  slightly  soluble  in 
cold,  more  readily  in  hot  water,  and  crystallizes  in  small  needles, 
which  melt  at  169° — 170°,  and  sublime  without  decomposition. 
Ferric  chloride  produces  a  brown  precipitate  in  a  concentrated 
solution ;  phosphorus  pentachloride  converts  it  into  the  chloride 
of  a-dichlorobenzoic  acid  (Lossner). 

Dichloroparahydroxylenzoic  acid,  C6H2C12(OH)C02H,  has  also 
been  prepared  by  Lossner ;  it  crystallizes  in  fine  needles,  which 
melt  at  255°— 256°. 

Dibromoparahydroxybenzoic  acid,  C6H2Br2(OH)C02H,  (3:5: 
4:1),  has  been  obtained  from  dibromanisic  acid.  It  is  scarcely 
soluble  in  water,  and  crystallizes  from  alcohol  in  needles,  which 
melt  with  decomposition  at  266° — 268°,  but  sublime  at  a  lower 
temperature.  A  monobromoparahydroxybenzoic  acid  is  not 
known;  when  bromine  water  is  added  to  a  solution  of  para- 

1  Bcr.  Deutsch.  Chem.  Gcs.  ii.  666. 

2  Lossner,  Journ.  Prakt.  Chem.  [2]  xiii.  432. 

3  Hasse,  Ber.  Deutsch.  Chem.  Ges.  x.  2192. 


CHLOROPARAHYDROXYBENZOIC  ACID.  335 

hydroxybenzoic  acid,- a  precipitate  of  tribromophenol  is  produced 
(Bar th  and  Hlasiwetz). 

lodoparahydroxylenzoic  acid,  2C6H3I(OH)CO2H  4-  H2O,  is 
formed  when  parahydroxybenzoic  acid  is  boiled  with  water;, 
iodine  and  iodic  acid ;  it  crystallizes  from  hot  water  in  small 
needles,  which  become  anhydrous  at  100°  and  then  melt  at 
1920.1 

Di-iodoparaliydroxybenzoic  acid,  C6H2T2(OH)C02H,  is  formed 
together  with  the  preceding  compound,  and  crystallizes  in  small 
needles,  which  are  scarcely  soluble  in  water,  but  readily  in 
alcohol. 

Nitroparahydroxylenzoic  acid,  C6H3(NO2)(OH)CO2H,  (3:4: 1). 
Griess  obtained  this  compound  by  the  action  of  boiling  potash  on 
3-nitro-amidobenzoic  acid.2  It  is  also  formed  in  small  quantity, 
together  with  /3-nitro-salicylic  acid,  by  heating  orthonitrophenol 
with  alcoholic  potash  and  tetrachloromethane  (Hasse).  It  crystal- 
lizes from  boiling  water  in  yellowish  needles,  melting  at  185°. 
Its  solution  is  not  coloured  by  ferric  chloride. 

Basic  barium  nitroparaTiydroxybenzoate,  C7H3N05Ba  +  H2O,  is 
obtained  by  adding  barium  chloride  to  a  hot,  ammoniacal  solu- 
tion of  the  acid.  It  forms  yellowish  red,  lustrous  plates. 

Dinitroparaliydroxybcnzoic  acid,  C6H2(NO2)9(OH)CO.,H,  (3:5: 
1:4)  is  formed  when  a  boiling  solution  of  dinitroparamidobenzoic 
acid  is  treated  with  nitrous  acid  or  with  caustic  potash.  It  is 
slightly  soluble  in  cold,  more  readily  in  hot  water,  and  crystallizes 
in  large,  thin  tablets,  which  are  coloured  light  yellow  to  bronze, 
and  melt  at  235°—  2370.3 

Its  salts  are  coloured  yellow  or  orange-  red,  and  crystallize 
well. 

Earth  has  prepared  a  mono-  and  a  di-  nitro-acid  by  the  action 
of  nitric  acid  on  parahydroxybenzoic  acid,  both  of  which  seem  to 
be  different  from  the  preceding  compounds. 

Amidoparafiydroxybenzoic  acid,  C6H3(NH2)(OH)C02H.  Barth 
obtained  this  substance  by  the  reduction  of  hisnitroparahydroxy- 
benzoic  acid.  It  crystallizes  in  needles  and  forms  a  sulphate 
which  also  crystallizes  in  needles,  and  gives  a  dark  cherry-red 
colouration  with  concentrated  nitric  acid. 

Sulphoparahydroxybenzoic  acid,  C6H3(SO3H)(OH)CO2H,  was 
prepared  by  Kolle  by  the  action  of  sulphur  trioxide  on  para- 

1  Pelzer,  Ann.  Chem.  Pharm.  cxlvi.  288. 

*  Ber.  Deutsch.  Chem.  Gcs.  v.  856. 

3  Salkowski,  Ann.  Chem.  Pharm.  clxiii.  36. 


336  AROMATIC  COMPOUNDS. 

hydroxybenzoic  acid.1  It  is  also  obtained  when  the  latter,  or 
parahydroxybenzide,  is  heated  with  concentrated  sulphuric  acid 
(Klepl),  and  forms  deliquescent  needles,  which  are  insoluble  in 
ether.  Its  solution  is  coloured  blood-red  by  ferric  chloride  ;  on 
fusion  with  potash,  it  yields  protocatechuic  acid. 

Acid  potassium  sulphoparahydroxylenzoate,  C7H5SO6K  +  H20, 
is  a  very  characteristic  salt,  since  it  is  even  less  soluble  in  water 
than  acid  potassium  tartrate.  It  crystallizes  from  a  hot  solution 
in  quadratic  tablets  or  prisms,  and  from  a  less  concentrated 
solution  in  rectangular  plates  which  are  obliquely  striated  (Klepl). 

Parahydroxylenzoyl  sulphuric  acid,  C6H4(S04H)CO2H,  occurs 
as  an  alkali  salt  in  the  urine  of  the  dog  after  administration  of 
parahydroxybenzoic  acid.  The  potassium  salt,  C6H4(SO4K)C02K, 
is  obtained  by  heating  an  alkaline  solution  of  parahydroxybenzoic 
acid  with  potassium  disulphate,  and  crystallizes  in  lustrous 
plates  or  .tablets,  which  decompose  at  250°  with  formation 
of  potassium  sulphate  and  anhydrides  of  parahydroxybenzoic 
acid.2 


SUBSTITUTION    PRODUCTS   OF  ANISIC    ACID. 

2187  Chloranisic  acid,  C6H3C1(OCH3)CO2H,  is  formed  by  the 
action  of  chlorine  on  fused  anisic  acid,  and  crystallizes  from  dilute 
alcohol  in  needles  or  rhombic  prisms,  which  melt  at  176°  and 
volatilize  without  decomposition.3 

Dichlor anisic  acid,  C6H2C12(OCH3)C02H,  is  obtained,  together 
with  chloranil,  by  heating  anisic  acid  with  hydrochloric  acid  and 
potassium  chlorate ;  it  crystallizes  from  alcohol  in  large  needles 
melting  at  1960.4 

Bromanisic  acid,  C6H3Br(OCH3)C02H,  is  formed  by  the  action 
of  bromine  on  anisic  acid  (Cahours),  the  latter  being  kept 
covered  with  hot  water.5  It  crystallizes  from  alcohol  in  needles 
which  melt  at  213° — 214°  and  sublime  in  small  plates. 

Dibromanisic  acid,  C6H2Br2(OCH3)CO2H.  Reinecke  pre- 
pared this  substance  by  heating  anisic  acid  to  120°  with  bromine 
and  water ;  it  crystallizes  in  long  needles  melting  at  207°.  On 

1  Ann.  Chem.  Pharm.  clxiv.  150. 

2  Baumann,  Ber.  Dcutsch.  Chem.  Ges.  xi.  1916. 
8  Cahours,  Ann.  Chem.  Pharm.  Ivi.  312. 

4  Reinecke,  Zcitschr.  Chem.  1866,  366. 

6  Salkow&ki,  Ber.  Dcutsch.  Chem.  Ges.  vii.  1013. 


IODANISIC  ACID.  337 


further  treatment  with  bromine,  tribromanisol  and  tetrabromo- 
quinone  are  formed,  while  fuming  nitric  acid  converts  it  into 
dibromonitro-anisol,  C6H2Br2(N02)OH,  (3:5:4: 1),  which  was 
previously  obtained  by  Korner  in  a  different  manner,  the  con- 
stitution of  the  acid  being  thus  shown.1  When  its  sodium  salt 
is  distilled  with  lime,  the  methyl  ether  is  formed,  together 
with  the  basic  sodium  salt  of  dibromoparahydroxybenzoic 

acid  : 2 

/C02Na  /C02.OCH3  /CO2Na, 

2C6H2Br2<  =  C6H2Br/  +  C6H2Br2<( 

\OCH3  \OCH3  XONa 

This  ether  crystallizes  from  alcohol  in  lustrous  needles  melting 
at  91-5°— 92°. 

The  dibromoparahydroxybenzoic  acid  is  also  obtained  by 
heating  dibromanisic  acid  with  hydriodic  acid.3 

lodanisic  acid,  C6H3I(OCH3)CO2H,  was  prepared  by  Griess 
from  diazo-amido-anisic  acid,4  while  Peltzer  obtained  it  by 
heating  anisic  acid  to  145° — 150°  with  iodine  and  iodic  acid.5  It 
crystallizes  from  alcohol  in  needles,  which  melt  at  234*5°,  and 
sublime  in  small  plates. 

Nitro-anisic  acid,  C6H3(NO2)(OCH3)C02H,  was  obtained  by 
Cahours  as  a  product  of  the  action  of  nitric  acid  on  anisic  acid 
and  anisol.6  In  order  to  prepare  it,  anisol  is  allowed  to  drop 
into  ten  times  its  weight  of  warm  nitric  acid,  of  specific 
gravity  1'4,  the  mixture  boiled  for  a  short  time,  and  the  acid 
then  precipitated  by  water ;  it  is  well  washed  and  finally  freed 
>m  an  admixed  oil  by  solution  in  ammonia  and  reprecipitation 
by  hydrochloric  acid.7  Nitro-anisic  acid  is  slightly  soluble  in 
water,  and  crystallizes  from  alcohol  in  compact  prisms  melting  at 
189°.  On  heating  with  water  to  220°,  it  decomposes  into  ortho- 
nitrophenol,  methyl  alcohol  and  carbon  dioxide,8  while  aqueous 
ammonia  at  140° — 170°  converts  it  into  S-nitro-amidobenzoic 
acid.9 

Its  salts  have  been  investigated  by  Engelhardt.10 
Dinitro-anisic  acid,  C6H2(NO2)2(OCH3)C02H.     Salkowski  and 
Rudolph  prepared  this  substance  by  dissolving   anisic  acid  in 

1  Balbiano,  Gaz.  Chim.  Ital.  xiv.  9.  2  Ibid.  xiii.  65. 

8  Alessi,  ibid.  xv.  242.  4  Ann.  Chem.  Pharm.  cxvii.  54. 

5  Ibid,  cxlvi.  302.  6  Cahours,  ibid.  xh.  71. 

7  Salkowski,  ibid,  clxiii.  6. 

8  Salkowski  and  Rudolph,  Ber.  Deutsch.  Chem.  Ges.  x.  1254. 

9  Salkowski,  Ann.  Chem.  Pharm.  clxxiii.  35. 
10  Zinin,  ibid.  xcii.  327  ;  Cahours,  ibid.  cix.  21. 


338  AROMATIC  COMPOUNDS. 

portions  of  40  grammes  at  a  time  in  a  well-cooled  mixture  of 
sulphuric  and  nitric  acids,  160  grammes  of  the  former  and  140 
of  the  latter  being  required  for  each  portion  of  anisic  acid  ; 
notwithstanding  the  low  temperature,  carbon  dioxide  is  evolved 
and  di-  and  tri-nitro-anisol  are  formed.  The  dinitro-anisic  acid 
separates  from  the  acid  solution  on  standing,  and  is  then  dissolved 
in  a  cold,  dilute  solution  of  sodium  bicarbonate,  re-precipitated 
by  alcohol  and  finally  purified  by  re-crystallization  from  dilute 
alcohol.  It  forms  yellowish  needles  melting  at  181° — 182°,  and 
on  boiling  with  caustic  soda  decomposes  into  methyl  alcohol  and 
dinitroparahydroxybenzoic  acid,  while  it  is  immediately  converted 
into  chrysanisic  acid  by  boiling,  concentrated  ammonia  (p.  258). 

Amido-anisic  acid,  C6H3(NH2)(OCH3)CO2H,  is  obtained  by 
reducing  nitre-anisic  acid  with  alcoholic  ammonium  sulphide.1 

It  is  slightly  soluble  in  water,  readily  in  alcohol,  and  crystal- 
lizes in  long,  thin,  four-sided  prisms,  which  melt  at  180°  and  are 
decomposed  into  carbon  dioxide  and  anisidine  when  heated  with 
caustic  baryta  (Part  III.  p.  249). 

Methyl  amido-anisate,  C6H3(NH2)(OCH3)C02.CH3,  was  pre- 
pared by  Cahours  from  the  methyl  ether  of  nitro-anisic  acid  by  re- 
duction ;  it  crystallizes  in  prisms  which  readily  dissolve  in  alcohol. 

Methylamido-anisic  acid,  C6H3(NH.CH3)(OCH3)CO2H.  Griess 
obtained  this  substance  by  heating  potassium  amido-anisate  with 
methyl  iodide.  It  is  slightly  soluble  in  hot  water  and  cold 
alcohol,  but  more  readily  in  hot  alcohol,  and  melts  above  20 0°.2 

Trimethylamido-anisic  acid,  or  Trim,ethylanise-betaine,CllH.l5NQ3 
+  5H20,  is  formed  by  the  action  of  methyl  iodide  and  caustic 
potash  on  anisic  acid,  and  crystallizes  from  water  in  well- 
formed,  vitreous  prisms,  which  have  a  bitter  taste  and  are  neutral 
to  litmus  paper. 

It  is  completely  converted  by  distillation  into  the  metameric 
methyl  ether  of  dimethylamido-anisic  acid  : 

/OCH3  /OCH3 

C6H3— CO-0  =  C6H  /  CO.OCH3. 
\      /  \N(CH3)2 

N  (CH3)3 

The  latter  substance  is  a  yellowish  liquid,  which  has  a  faint 
aromatic  odour  and  boils  at  2880.3 

1  Zinin,  Ann.  Chem.  Pkarm.  xcii.  327  ;  Cahours,  ibid.  cix.  21. 

2  Bcr.  Deutsch.  Chem.  Ges.  v.  1042. 
8  Griess,  ibid,  vi.  587. 


ANISENYLOXIME  COMPOUNDS.  339 


ANISENYLOXIME  COMPOUNDS. 

2188  These  bodies,  which  correspond  to  the  benzenyloxime 
compounds  (p.  207),  are  prepared  in  an  exactly  similar  manner, 
anisyl  chloride  being  gradually  added  to  a  solution  of  hydroxyl- 
amine  hydrochloride,  which  is  kept  faintly  alkaline  by  the  addition 
of  dilute  carbonate  of  soda  solution.  A  mixture  of  anishydrox- 
amic  acid,  di-anishydroxamic  acid  and  anisic  acid  is  thus 
obtained.  Boiling  water  extracts  from  this  a  portion  of  the 
anisic  acid  and  all  the  anishydroxamic  acid,  these  being  sub- 
sequently separated  by  means  of  their  barium  salts,  that  of  the 
former  being  soluble  while  that  of  the  latter  is  insoluble  in  water. 
The  dry  mixture  of  the  two  acids  may  also  be  extracted  with 
warm  absolute  ether,  in  which  anishydroxamic  acid  is  almost 
insoluble.  The  di-anishydroxamic  and  anisic  acids  are  separated 
by  treatment  with  a  cold  solution  of  sodium  carbonate,  which 
lissolves  the  latter  completely,  while  only  a  small  portion  of  the 
former  enters  into  solution.  The  liquid  is  filtered  rapidly, 
tuse  di-anishydroxamic  acid  is  easily  decomposed  by  carbon - 
ite  of  soda,  the  filtrate  almost  neutralized  with  hydrochloric 
nd,  and  then  saturated  with  carbon  dioxide,  all  the  di-anis- 
hydroxamic acid  present  being  thus  precipitated.1 

Anishydroxamic  acid,  .  CH3O.C6H4.C(OH)NOH,  is  slightly 
)luble  in  cold,  readily  in  hot  water  and  alcohol,  but  is  almost 
insoluble  in  ether ;  it  crystallizes  in  small  plates,  melting  at 
156° — 157°,  and  is  coloured  deep  violet  by  ferric  chloride.  The 
acid  potassium  salt,  C8H8KNO3  +  C8H9N03,  forms  long,  flat 
needles,  which  are  tolerably  soluble  in  cold  water.  Lead  acetate 
produces  a  thick,  white  precipitate  2  of  C2H3O2PbC8H8NO3. 

Ethyl  anishydroxamate,  CH3O.C6H4.C(OH)NOC2H5,  is  formed 
by  the  action  of  anisyl  chloride  on  ethylhydroxylamine ;  it  is 
insoluble  in  water,  readily  soluble  in  alcohol,  less  easily  in  ether, 
from  which  it  crystallizes  in  tablets,  which  melt  at  84°  and 
have  feeble  acid  properties.  On  heating  with  concentrated 
hydrochloric  acid,  it  is  split  up  into  anisic  acid  and  ethyl- 
hydroxylamine.3 

Ethylanishydroxamic    acid,     CH3O.C6H4.C(OC2H6)NOH,     is 

1  Lessen,  Ann.  Chem.  Pharm.  clxxv.  234. 

2  Hodges,  ibid,  clxxxii.  218. 

3  Pieper,  ibid,  ccxvii.  16. 


340  AROMATIC  COMPOUNDS. 

obtained  by  heating  the  ethyl  ether  of  anisbenzhydroxamic 
acid  with  caustic  potash.  It  is  precipitated  by  carbon  dioxide 
as  an  oily  liquid,  which  solidifies  to  a  crystalline  mass,  melting 
at  32°.  It  is  readily  soluble  in  alcohol  and  ether,  and  decomposes 
on  heating  with  hydrochloric  acid  into  ethyl  anisate  and 
hydroxylamine.1 

Dianishydroxamic  acid,  CH3O.C6H4.C(NO.CO.C6H4.OCH3)OH, 
is  scarcely  soluble  in  water  and  ether,  slightly  in  alcohol, 
and  crystallizes  in  needles,  melting  at  142° — 143°.  It  is  de- 
composed by  baryta  water  into  anisic  acid  and  anishydroxamic 
acid. 

Benzaniskydroxamic  acid,  C6H5.C(NO.CO.C6H4.OCH3)OH,  is 
formed  by  heating  benzhydroxamic  acid  to  100°  with  anisyl 
chloride.  It  crystallizes  from  alcohol  in  needles  or  prisms,  which 
melt  at  131° — 132°.  On  heating  with  baryta  water,  it  decom- 
poses into  anisic  acid  and  benzhydroxamic  acid,  while  boiling 
water  splits  it  up  into  carbon  dioxide,  anisic  acid  and  diphenyl 
urea.  When  heated  alone,  it  yields  carbon  dioxide,  phenyl 
isocyanate,  anisic  acid  and  anisanilide,C6H5.NH(CO.C6H4.OCH3). 

a-Ethylbenzanishydroxamate^  or  Benzanisethylhydroxylamine, 
C6H5.C(NO.CO.C6H4.OCH3)OC2H5,  is  obtained  by  the  action  of 
ethyl  iodide  on  silver  benzanishydroxamate.  It  crystallizes  from 
a  mixture  of  ether  and  benzene  in  thick,  monoclinic  tablets, 
melting  at  74°  (Pieper).  It  is  decomposed  by  caustic  potash 
into  anisic  and  a-ethylbenzhydroxamic  acids,  and  by  hydrochloric 
acid  into  anisic  acid,  ethyl  benzoate  and  hydroxylamine. 

ft-Ethylbenzanishydroxamate  is  formed  by  the  action  of  anisyl 
chloride  on  a-  or  /3-ethylbenzhydroxamic  acid,  and  separates  from 
ether  in  monoclinic  crystals,  melting  at  89°.  On  heating  with 
concentrated  caustic  potash  solution,  it  decomposes  into  anisic 
acid  and  /3-ethylbenzhydroxamic  acid,  while  on  dry  distillation 
it  decomposes  into  benzonitril,  anisic  acid  and  aldehyde. 

Anisbenzhydroxamic  acid,  CH3O.C6H4C(NO.CO.C6H5)OH,  is 
obtained  from  anishydroxamic  acid  and  benzoyl  chloride;  it 
crystallizes  in  needles  or  prisms,  which  melt  at  147° — 148°,  and 
decompose  at  a  higher  temperature  into  carbon  dioxide,  benzoic 
acid,  anisol  isocyanate,  CON.C6H4.OCH3,  and  benzoylanisidine, 
NH(CO.C6H5)C6H4.OCH3. 

Ethyl     anisbenzhydroxamate,   or    Anisoenzethylhydroxylamine, 
CH3O.C6H4C(NO.CO.C6H5)OC3H5,  crystallizes   in    short,   four- 
sided,  asymmetric  pyramids,  melts  at  79°  and  is  decomposed 
1  Eisler,  Ann.  Chem.  Pharm.  clxxv.  338. 


DIBENZANISHYDROXYLAMINE.  341 

by  caustic    potash  into   benzole  acid  and  ethylanishydroxamic 
acid. 

Benzethylanishydroxylamine,  C6  H5  C(N  O  C  2  H  5)O.  C  O.C  6  H  4. 
OCH3,  is  obtained  by  the  action  of  anisyl  chloride  on  the  silver  salt 
of  ethylbenzhydroxamate,  and  separates  from  ether  in  asymmetric 
crystals,  melting  at  64°.  It  is  decomposed  by  highly  concentrated 
caustic  potash  into  anisic  acid  and  ethylbenzhydroxamate. 


is  formed  when  a  solution  of  ethylanishydroxamate  in  caustic 
potash  is  treated  with  benzoyl  chloride,  and  forms  monosymmetric 
crystals,  melting  at  93° — 94°.  It  is  split  up  into  benzoic  acid 
and  ethyl  anishydroxamate  on  heating  with  caustic  potash.1 

2189  Hydroxylamine  Derivatives  containing  three  Acid  Radicals 
are  formed  by  the  action  of  anisyl  or  benzoyl  chloride  on  the 
silver  salts  of  the  dihydroxamic  acids.  They  are  insoluble  in 
water  and  sodium  carbonate  solution,  and  only  very  slightly 
soluble  in  cold  alcohol.  On  heating  with  hydrochloric  acid,  the 
radical  which  was  last  introduced  is  split  off.2 

^NO.CO.C6H5 

DlBEXZANISHYDROXYLAMINE,  C6H5C\ 

XO.CO.C6H4.OCH3 

Melting-point. 

a)  Long,  monosymmetric  needles  or  prisms  .  110° — 110'5° 
/S)  Small  crystals 109°— 110° 


4  OCH3 
BENZANISBENZHYDROXYLAMINE,  C6H5.C 

\O.CO.C6H5 

Melting-point. 

a)     Short,  asymmetric  prisms 113° — 114° 

/?)     Long,  rhombic  prisms 124° — 125° 

7)     Monosymmetric  tablets ;  decompose  on  fusion 


jsro.co.c6H5 

ANISDIBENZHYDROXYLAMINE,  CH3O.C6H4C\ 

\OCO.C6H6 

Melting-point. 

a)     Lustrous  monoclinic  tablets 137° — 137'5 

£)     Very  small  crystals,  usually  opaque      .    .    .    109'5° — 110'5 

1  Pieper,  Ann.  Chcm.  Pharm.  ccxvii.  1.  2  Lessen,  ibid,  clxxxvi.  1. 

253 


342  AROMATIC  COMPOUNDS. 


ANISBENZANISHYDROXYLAMINE, 

NO.CO.C6H6 

CH3O.C6H4.Cf 

\OCO.C6H4.OCH3 

Melting-point. 

a)     Very  small,  monosymmetric  tablets  ....       152° — 153° 
ft)     Monosymmetric  tablets 148°— 149° 


DlANISBENZHYDROXYLAMINE, 

/NO.CO.C6H4.OCH3 
CH3O.C6H4.C<f 

\OCO.C6H6 

Melting-point. 
Large,  monosymmetric  crystals  with  many  faces    .     147'5C 


-o 


^NO.CO.C6H4.OCH3 
BENZDIANISHYDROXYLAMINE,  C6H5.Cr^ 

\O.CO.C6H4.OCH3 

Melting-point. 
a)     Sbort,  asymmetric  columns    .......   137'5° — 138'5° 

ft)     Asymmetric  tablets 137-5°— 138° 

Lossen  remarks  concerning  these  compounds :  "  The  twelve 
substances  described  above  afford  an  additional  proof  of  the  well- 
established  fact  that  there  are  two  kinds  of  isomerism,  which 
must  be  carefully  distinguished  from  one  another.  Seven 
isomeric  substances  were  obtained  as  the  products  of  three 
different  methods  of  preparation,  three  being  yielded  by  one 
method  and  two  by  each  of  the  others ;  three  further  methods 
of  preparation,  different  from  the  preceding,  gave  five  isomeric 
bodies,  two  being  formed  by  each  method.  Isomerides  are, 
therefore,  formed  both  by  different  methods  and  by  one  and  the 
same  method,  but  the  difference  between  two  compounds  which 
are  prepared  by  independent  methods  is  not  the  same  as  that 
existing  between  the  isomeric  products  of  a  single  method."  ] 

The  latter,  in  fact,  always  give  the  same  decomposition 
products  on  treatment  with  hydrochloric  acid  or  caustic  potash. 
1  Loc.  cit.  and  Ber.  Deutsch.  Chem.  Ges.  xviii.  1189. 


PKOTOCATECHUICALDEHYDE.  343 

Thus  benzole  acid  and  dianishydroxamic  acid  are  obtained  by 
the  action  of  caustic  potash  upon  the  anisbenzanishydroxylamines, 
the  same  products,  together  with  anisic  acid  and  anisbenzhydrox- 
amic  acid,  being  also  formed  from  dianisbenzhydroxylamine, 
while  the  benzdianishydroxylamines  are  resolved  into  anisic  acid 
and  benzanishydroxamic  acid. 

The  dibenzanishydroxylamines  under  the  same  circumstances 
yield  benzanishydroxamic  acid,  and  not,  as  might  have  been 
expected,  a  compound  metameric  with  this  : 

NO.CO.C6H5 

C6H6.cf  +2KOH  = 

\O.CO.C7H70 

NOK 

C6H5.C<f  +  KO.CO.C6H5  +  H20. 

\O.CO.C7H70 

Lossen  assumes  that  the  decomposition  first  proceeds  in  this 
way,  and  that  the  compound  formed  changes  into  : 


"  A  similar  exchange  between  a  metal  and  an  acid  radical  has 
often  been  observed." 


DIHYDROXYBENZYL   AND   DIHYDROXY- 
BENZOYL,  COMPOUNDS. 

2190  Protocatechuicaldehyde,  or  a-Orfhodihydroxybenzaldehyde, 
C6H3(OH)2CHO.(COH  :  OH  :  OH  =  1 :  3  :  4),  was  first  prepared 
from  piperonal  (p.  347)  and  from  vanillin  or  its  methyl  ether. 
Tiemann  and  Reimer  found  that  it  is  also  formed  by  the  action 
of  chloroform  on  an  alkaline  solution  of  catechol.1  In  order  to 
prepare  it,  a  solution  of  10  parts  of  the  latter  in  600  parts  of  16 
per  cent,  caustic  soda  solution  is  heated  for  5 — 6  hours  with  100 
parts  of  chloroform  in  an  apparatus  connected  with  an  inverted 
condenser,  acidified  with  hydrochloric  acid,  allowed  to  cool, 
filtered  from  a  black  resinous  substance  and  shaken  out  with 
1  Be,r.  Deutsch.  Chem.  Ges.  ix.  1269. 


314  AROMATIC  COMPOUNDS. 

ether.  The  aldehyde  is  extracted  from  the  ethereal  solution  by 
means  of  acid  sodium  sulphite,  liberated  by  dilute  sulphuric 
acid,  again  dissolved  in  ether  and  the  residue  on  evaporation 
re- crystallized  from  boiling  toluene.1 

It  is  readily  soluble  in  water,  alcohol  and  ether,  very  slightly 
in  cold,  more  readily  in  boiling  toluene,  and  crystallizes  from 
water  in  flat,  lustrous  needles,  melting  at  150°.  Ferric  chloride 
added  to  its  aqueous  solution  produces  a  green  colouration,  which 
becomes  first  violet  and  then  red  on  the  addition  of  sodium 
carbonate.  Ammoniacal  silver  solution  is  immediately  reduced 
by  it. 

Vanillin,  C6H3(OH)(OCH3)CHO(CHO  :  OCH3:OH  =  1 : 3  :  4). 
The  crystalline  coating  of  vanilla  (givre  de  vanille)  was  mistaken 
by  Buchholz  for  benzoic  acid,  and  by  other  chemists  for  cinnamic 
acid,  although  Bley  had  previously  pointed  out  that  it  is  a 
distinct  substance.  Gobley,  who  at  first  took  it  for  cumarin, 
subsequently  found  with  Vee,  that  it  differs  from  this  substance, 
and  named  it  vanillin,2  while  Stokkebye,  who  obtained  analytical 
results  differing  from  those  of  Gobley,  termed  it  vanillaic  acid.3 

The  correct  formula  of  vanillin  was  determined  by  Carles,  who 
investigated  its  properties  and  some  of  its  derivatives,4  without 
being  able  to  determine  its  relations  to  any  known  compounds. 
Tiemann  and  Haarmann,  however,  were  successful  in  this,  and 
prepared  it  artificially  from  coniferin,  C1GH12O8.  This  compound 
occurs  in  the  cambium  sap  of  the  fir-tree,  and  is  decomposed  by 
emulsin  in  the  presence  of  water  into  grape  sugar  and  the 
compound  C10H12O3,  forming  odourless  crystals,  which  after 
standing  in  the  air  for  some  time  have  a  faint  smell  of  vanilla  ; 
Tiemann  and  Haarmann  therefore  oxidized  it  with  chromic  acid 
and  thus  obtained  vanillin.  On  fusion  with  caustic  potash  it  is 
converted  into  protocatechuic  acid,  and  on  heating  to  200°  with 
hydrochloric  acid  is  decomposed  into  methyl  chloride  and  proto- 
catechuicaldehyde,  proving  that  it  is  the  methyl  ether  of  the 
latter.5 

Reimer  and  Tiemann  then  obtained  it  by  heating  guaiacol 
(Part  III.  p.  134)  with  caustic  soda  and  chloroform,6  the  iso- 
meric  metamethoxysalicylaldehyde  being  simultaneously  formed 
(Tiemann  and  Koppe).7 


1  Tiemann  and  Koppe,  Per.  Deutsch.  Chem.  Ges.  xiv.  2015. 

2  Jahresber.  Chcm.  1858,  534.  3  Ibid.  1864,  512. 

4  Bull.  Soc.  Chim.  xvii.  2.  8  Scr.  Deutsch.  Chem.  Ges.  vii.  608. 

8  Ibid.  ix.  424.  7  Ibid.  xiv.  2023. 


VANILLIN.  345 


The  decomposition  product  of  coniferin,  referred  to  above,  is 
coniferyl  alcohol,  C6H3(OH)(OCH3)CHz=CH.CH2OH,  and  its 
conversion  into  vanillin  by  oxidation  may  readily  be  under- 
stood. The  latter  is  formed  in  a  similar  manner  from  eugenol, 
C6H3(OH)(OCH3)CH=CH.CH3,  a  substance  which  is  found  in 
oil  of  cloves. 

Vanilla  contains  1*5 — 2'5  per  cent,  of  vanillin  and  a  little 
vanillic  acid,  C6H3(OH)(OCH3)C02H,  but  no  other  aromatic 
compounds.1  It  also  occurs  in  Siam  benzoin,2  in  Asa  fcetida,3 
and  frequently  in  small  quantities  in  beet-sugar,4  since  the  sugar 
beet  contains  coniferin,  which  has  also  been  found,  together  with 
vanillin,  in  asparagus.5 

It  is  best  obtained  from  coniferin.  The  trees  containing  this 
substance,  Abies  excelsa,  A.  pectinata,  Pinus  strdbus,  P.  cembra, 
Larix  europaea,  and  other  pines  and  firs,  are  felled  during  the 
spring  or  early  summer.  The  trunks  are  then  sawn  into  pieces 
and  freed  from  bark,  the  cambium  sap  being  removed  by 
means  of  a  sharp  knife.  This  is  boiled  with  water,  freed  from 
albumen,  and  the  clear  liquid  evaporated  to  one-fifth  of  its  bulk. 
The  crystals  which  separate  after  some  time  are  filtered  off, 
pressed  and  re-crystallized  after  having  been  boiled  with  animal 
charcoal. 

The  aqueous  solution  is  then  allowed  to  flow  into  a  warm 
mixture  of  potassium  dichromate  and  dilute  sulphuric  acid, 
the  whole  being  heated  for  several  hours  in  a  flask  con- 
nected with  an  inverted  condenser.  After  cooling,  the  solution 
is  filtered  to  remove  a  small  quantity  of  a  resinous  substance 
and  extracted  with  ether.  On  evaporation  a  yellow  oil  is  left, 
which  solidifies  after  some  days  to  crystals  which  are  boiled  with 
animal  charcoal  and  re-crystallized  from  hot  water.6 

Vanillin  can  also  be  readily  obtained  by  replacing  the  nitroxyl 
group  in  paranitromethylmetahydroxybenzaldehyde  by  hydroxyl} 
by  the  oxidation  of  ferulaic  acid,  C6H3(OH)(OCH3)CH2.C()X 
which  can  be  prepared  on  the  large  scale  without  difficulty,7  and 
from  olivil,8  C14H18O5,  the  crystalline  constituent  of  the  Lecca 
gum,  or  resin  of  the  wild  olive,  which  is  used  in  Italy  as 

Tiemann  and  Haarmann,  Ber.  Deutsch.  Chem.  Ges.  viii.  1118  ;  ix.  1287. 

Jannaschand  Rump,  ibid.  xi.  1635. 

E.  Schmidt,  ibid.  xix.  Ref.  706. 

Scheibler,  ibid.  xiii.  335  ;  Lippmann,  ibid.  xiii.  662. 

Lippmann,  ibid.  xvi.  44  ;  xviii.  3335. 

Tiemann  and  Haarmann,  ibid.  vii.  609  and  614. 

7  M.  Ulrich,  ibid,  xviii.  Ref.  682. 

8  Scheidel,  ibid,  xviii.  685. 


346  AROMATIC  COMPOUNDS. 

incense.1      This   substance   will    be    further     described    along 
with  eugenol. 

Properties. — Vanillin  forms  white  needles,  generally  occurring 
in  stellate  aggregates,  which  possess  a  very  strong  taste  and  smell 
of  vanilla.  It  melts  at  80°— 81°,  sublimes  readily,  boils  at  285° 
without  decomposition  when  heated  in  an  atmosphere  of  carbon 
dioxide,  and  dissolves  in  90 — 100  parts  of  water  at  14°,  and  in  20 
parts  at  75° — 80°.  It  is  scarcely  soluble  in  cold,  more  readily  in 
hot  petroleum  spirit.  Its  aqueous  solution  is  coloured  bluish 
violet  by  ferric  chloride  ;  if  this  solution  be  heated,  white  needles 
of  dihydrovanillin  separate  out.  This  body,  which  will  be 
described  among  the  compounds  containing  two  aromatic  nuclei, 
has  the  following  constitution  : 2 

C6H2(OHXOCH3)CHO 
C6H2(OH)(OCH3)CHO' 

Vanillin  is  reduced  in  dilute  alcoholic  solution  by  sodium 
amalgam  to  vanillyl  alcohol,  C6H3(OH)(OCH3)CH2.OH,  which 
crystallizes  in  prisms,  melting  at  1150.3 

Vanillin  has  an  acid  reaction  and  forms  salts,  which  have 
been  investigated  by  Carles,  and  by  Tiernann  and  Haarmann ; 
the  former  has  also  prepared  bromine  and  iodine  substitution 
compounds. 

2191  Isovanillin,  C6H3(COH)(OH)(OCH3)  (1:  3:  4),  is 
formed  by  heating  opianic  acid,  C6H2(COH)(OCH3)2CO2H,  to 
160° — 170°  with  dilute  hydrochloric  acid  ;  it  crystallizes  from  hot 
water  in  monosymmetric  prisms,  which  possess  a  vitreous  lustre, 
and  its  solution  is  not  coloured  by  ferric  chloride ;  it  sublimes 
when  heated,  undergoing  slight  decomposition ; 4  its  vapour  has 
a  pleasant  smell,  resembling  that  of  vanilla  and  anise. 

Mcthylvanillin,  or  Dimethylprotocatechuicaldehyde,  C0H3(OCH3)2 
CHO,  is  formed  by  heating  potassium  vanillin  with  methyl 
iodide  and  wood-spirit.5  Beckett  and  Wright  prepared  it  by 
distilling  opianic  acid  with  soda  lime.6  It  is  slightly  soluble  in 
hot  water,  readily  in  alcohol,  and  crystallizes  in  needles,  which 
smell  like  vanilla ;  it  melts  at  42°— 43°  and  boils  at  280°— 285°. 

1  Pelletier,  Ann.  Chem.  Pharm.  vi.  31  ;  Sobrero,  ibid.  liv.  67. 
Tiemann,  Ber.  Deutsch.  Chem.  Gcs.  xviii.  3493. 
Ibid.  viii.  1125  ;  ix.  415  ;  xviii.  1597. 
Wegscheider,  Monatsch.  Chem.  iii.  789. 
Tiemann,  Ber.  Deutsch.  Chem.  Ges.  viii.  1135- 
Journ.  Chem.  Soc.  1876,  i.  287. 


VANILLIN  COMPOUNDS.  347 

Acetylvanillin,  C6H3(OCO.CH3)(OCH3)CHO,  is  obtained  by 
the  action  of  sodium  vanillin  .on  an  ethereal  solution  of  acetic 
anhydride.  It  crystallizes  in  large,  flat  needles,  melting  at  770.1 

Glucovanttlin,  or  Vanillin  glucoside,  C6H3(OCH3)(OC6HUO5) 
CHO  +  2H00,  is  formed  by  the  oxidation  of  coniferin  with  a 
dilute  solution  of  chromic  acid.  It  is  tolerably  soluble  in  water, 
less  readily  in  alcohol,  and  crystallizes  from  dilute  alcohol  in 
white  needles  which  lose  their  water  at  100°  and  melt  at  192°.  It 
is  readily  decomposed  by  emulsin  into  grape  sugar  and  vanillin, 
and  is  converted  by  sodium  amalgam  and  water  into  glucovanillyl 
alcohol,  C6H3(OCH3)(OC6HnO5)CH2.OH  +  H2O,  which  crys- 
tallizes in  white  needles,  melting  at  120°.  When  its  aqueous 
solution  is  treated  with  a  little  emulsin  and  allowed  to  stand  for 
four  or  five  days  at  30° — 40°,  vanillyl  alcohol  is  formed,  and  can 
most  easily  be  obtained  pure  by  this  method.2 

Piperonal,  or  Methyleneprotocatechuicaldehyde,  C6H3(O2CH2) 
CHO,  was  prepared  by  Fittig  and  Mielk  by  the  oxidation  of 
piperic  acid,  C6H3(02CH2)C4H4.CO2H,  with  potassium  per- 
manganate.3 It  is  slightly  soluble  in  cold,  more  readily  in  hot 
water  and  forms  long,  thin,  lustrous  plates,  which  have  a  very 
pleasant  smell,  resembling  that  of  the  heliotrope  ;  4  it  is  on  this 
account  employed  in  perfumery.5 

Piperonal  melts  at  37°,  boils  at  263°  and  forms  a  vapour  which 
has  a  specific  gravity  of  5'18.6  A  very  characteristic  reaction  of 
this  substance  is  that  it  decomposes  into  protocatechuicaldehyde 
and  finely  divided  carbon  when  it  is  heated  to  200°  with  dilute 
hydrochloric  acid : 7 

/CHO  /CHO 


Oxidizing  agents  convert  it  into  piperonylic  acid,  while  sodium 
amalgam  reduces  it  in  boiling  aqueous  solution  to  piperonyl 

1  Tiemann  and  Nagai,  Ber.   Deutsch.  Chem.  Ges.  xi.  647. 
Tiemann,  ibid,  xviii.  1595.  »  Ann.  Chem.  Pharm.  clii.  35. 

*  This  same  smell  is  possessed  by  "vanillon,"  a  kind  of  vanilla,  which  forms 
thick,  fleshy  capsules,  and  is  obtained  from  the  West  Indies.  It  is  only  employed 
in  perfumery  for  the  preparation  of  essence  of  heliotrope  ;  it  contains  no  piperonal, 
but  vanillin  and  an  oil  which  is  probably  benzaldehyde.  The  perfumers  in 
preparing  essence  of  heliotrope  add  a  little  of  this  oil  to  the  extract  of  vanillon. 
If  a  little  be  added  to  a  solution  of  pure  vanillin,  both  substances  can  be 
recognized  by  their  smell  for  some  time,  but  after  standing  for  months,  the 
mixture  acquires  the  smell  of  heliotrope  (Tiemann  and  Haarmann,  Ber.  Deutsch. 
Chem.  Ges.  ix.  1287.)  *  Chem.  Zeit.  1884,  173. 

5  Knecht,  Ber.  Deutsch.  Chem.  Ges.  x.  1274. 

7  Fittig  and  Kem.sen,  Ann.  Chem.  Pharm.  clxviii.  97. 


348  AROMATIC  COMPOUNDS. 

alcohol,  C6H3(O2CH2)CH2.OH,  which  is  slightly  soluble  in  cold, 
more  readily  in  hot  water,  and  forms  long,  colourless  crystals, 
melting  at  5 10.1 

Dicliloropiperonal,  C6H3(O2CC12)COH.  When  one  molecule 
of  piperonal  is  heated  with  three  molecules  of  phosphorus 
pentachloride,  the  compound  C6H3(O2CC12)CHC12  is  formed. 
It  is  an  oily  liquid,  which  is  decomposed  by  water  into  hydro- 
chloric acid  and  dichloropiperonal ;  the  latter  crystallizes  from 
toluene  in  needles,  which  melt  at  90°  and  undergo  the  following 
decomposition  when  heated  with  water  : 

/CHO  /CHO 

C6H3^  )\ccla  +  2H20  =  C6H3^(    [  +  C02  +  2HC1. 

Protocatechuicaldehyde  was  first  prepared  according  to  this 
method  by  Fittig  and  Remsen. 

2192  /3  Methylorthodihydroxybenzaldehydc,  or  (B-Metamethoxy- 
salicylaldehyde,  C6H3(OH)(OCH3)CHO  (CHO:  OH:  OCH3= 
t  :  2 :  3),  is  formed  together  with  vanillin  by  heating  guaiacol 
with  caustic  soda  and  chloroform.  On  distillation  with  steam  it 
passes  over  first  as  a  liquid,  which  smells  like  salicylaldehyde, 
boils  at  264° — 265°  in  a  current  of  carbon  dioxide,  stains  the 
skin  yellow  and  forms  a  deep  yellow  solution  in  alkalis.  Ferric 
chloride  added  to  an  alcoholic  solution  produces  a  green  coloura- 
tion containing  a  shade  of  violet.2 

Metadihydroxybenzaldchyde,  or  (3-Rcsorcylaldehyde,  C6H3(OH)2 
CHO  (CHO  :  HO  :  HO  =  1 :  2  :  4),  is  obtained,  along  with 
resorcyldialdehyde,  C6H2(OH)2(CHO)2,  by  heating  resorcinol 
with  caustic  soda  and  chloroform.3  It  crystallizes  from  water  in 
yellowish  needles,  which  melt  at  134° — 135°;  its  solution  is 
coloured  reddish  brown  by  ferric  chloride.  It  is  an  unstable 
substance  and  gradually  decomposes  in  moist  air  into  a  red 
powder. 

Orthomethoxyparahydroxybenzaldehyde,  C6H3(OH)(OCH3)CHO 
(CHO :  OCH3 :  OH  =  1  :  2  :  4),  is  formed,  together  with  the 
following  compound  and  two  resorcyldiaidehydes,  by  heating 
methylresorcinol  with  caustic  soda  and  chloroform.4  It  is  readily 
soluble  in  alcohol,  slightly  in  water  and  benzene,  and  crystallizes 

1  Fittig  and  Remsen,  Ann.  Chan.  Pharm.    clix.  138. 

2  Tiemann  and  Koppe,  Her.  Deutsch.  Chem.  Ges.  xiv.  2020. 

3  Tiemann  and  Lewy,  ibid.  x.  2212. 

4  Tiemann  and  Parrisius,  ibid.  xiii.  2365. 


PARAMETHOXYSALICYLALDEHYDE.  349 

from  the  latter  in  lustrous  plates  melting  at  153°.  Its  aqueous 
solution  is  coloured  a  faint  violet  by  ferric  chloride.  The  acetyl- 
derivative,  C6H3(OC2H30)(OCH3)CHO,  is  formed  by  adding  the 
potassium  compound  to  an  ethereal  solution  of  acetic  anhydride  ; 
it  crystallizes  in  needles,  melting  at  86°. 

Paramethoxysalicylaldchyde,  (COH:  OH:  OCH3  =  1:  2:  4), 
may  also  be  obtained  by  heating  7-resorcyldialdehyde  with  caustic 
potash  and  methyl  iodide.  It  is  almost  insoluble  in  water  and 
crystallizes  in  plates,  which  have  a  characteristic,  pleasant, 
aromatic  odour,  melt  at  62° — 63°  and  are  very  readily  volatile. 
It  forms  an  intensely  yellow  solution  in  alkalis ;  ferric  chloride 
produces  a  deep  reddish  yellow  colouration  in  an  alcoholic 
solution. 

Melting-point. 

Dimethyl-/3-resorcylaldehyde,  needles 68° — 69°. 

Diethylr/3-resorcylaldehyde,  lustrous  plates  .    .    .  71° — 72°. 

Paradihydroxybenzaldeliyde,  or  Gentisinaldehyde,  (CHO  :  OH  : 
OHz=l  :  2 :  5),  has  been  prepared  from  quinol  by  the  action  of 
chloroform  and  caustic  soda.  It  is  readily  soluble  in  water  and 
alcohol,  and  crystallizes  in  flat,  lustrous  yellow  needles,  melting 
at  99° ;  its  aqueous  solution  is  coloured  a  transient  bluish  green 
by  ferric  chloride  and  intensely  yellow  by  alkalis.1 

MethylparadiJiydroxylenzaldehyde,  or  Metamethoxysalicylalde- 
hyde,  (CHO  :  OH  :  OCH3=1  :  3  :  5),  has  been  obtained  from 
methylquinol.2  It  is  a  yellow  oil  which  has  an  aromatic  odour, 
solidifies  in  a  freezing  mixture  to  a  radiating  mass  and  then  melts 
at  4°;  it  boils  at  247° — 248°  in  a  current  of  carbon  dioxide.  It 
stains  the  skin  yellow,  forms  an  intensely  yellow  solution  in 
alkalis  and  in  alcoholic  solution  is  coloured  a  permanent  bluish 
green  by  ferric  chloride.  Its  acetyl-compound  crystallizes  in 
needles,  melting  at  63°. 

Melting- 
point. 

Dimethylparadihydroxybenzaldehyde,  fine  needles   .     .51° 
Ethylparadihydroxybenzaldehyde,  thick, yellow  prisms.  51 '5° 
Diethylparadihydroxybenzaldehyde,  small  needles  3  .     .  60° 

1  Tiemann  and  Miiller,  Ber.  Deutsch.  Chem.  Ges.  xiv.  1986. 

2  Ibid.  1990. 

3  Hantzsch,  Journ.  Prakt.  Chem.  [2]  xxii.  464. 


350  AROMATIC  COMPOUNDS. 


/OH 

DIHYDROXYBENZOIC  ACIDS,  C6H/-CO.OH 

\OH. 

2193  The  numbers  appended  designate  the  positions  of  the 
groups  C02H:  OH:  OH. 


PROTOCATECHUIC  ACID,  OR  ORTHODIHYDROXYBENZOIC 
-    ACID  (1:3:4). 

In  the  year  1859,  Hesse,  by  the  action  of  bromine  on  an 
aqueous  solution  of  quinic  acid,  C7H12O6,  obtained  "  carbohydro- 
kinonic  acid,"  C7H6O4,  which  decomposed  into  hydroquinone 
and  carbon  dioxide  on  heating.1  Two  years  later  Strecker  found 
that  an  acid  is  formed  by  fusing  piperic  acid  with  potash,  which 
resembles  catechuic  acid  so  closely  that  he  at  first  thought  that 
they  were  identical,  but  as  he  subsequently  found  less  carbon  in 
the  new  compound  he  named  it  protocatechuic  acid.2  It  decom- 
poses on  heating  into  carbon  dioxide  and  catechol,  and  should 
therefore  be  isomeric  with  Hesse's  acid.  All  the  other  properties 
of  the  two  acids,  however,  agreed  so  completely  that  most 
chemists  assumed  their  identity,  the  more  so  as  catechol  had  been 
previously  found  among  the  decomposition  products  of  carbo- 
hydrokinonic  acid.  Fittig  and  Macalpine  then  proved  decisively 
that  they  are  identical,  and  that  the  differences  observed  by 
Hesse  were  due  to  some  error.3 

Protocatechuic  acid  has  been  obtained  from  various  carbon 
compounds  by  fusion  with  caustic  potash.  Catechin  or  catechuic 
acid,4  the  maclurin  which  occurs  in  fustic,5  and  the  luteolin 
obtained  from  woad  also  yield  phloroglucinol,  while  many  resins 
give  parahydroxybenzoic  acid  in  addition  6  (p.  326). 

Its  synthetical  formation  from  sulphanisic  acid,7  paracresol- 

1  Ann.  Chem.  Pharm.  cxii.  52  ;  cxxii.  221. 

2  Ibid,  cxviii.  280.  Strecker  supposed  that  catechu  contained  two  homologous 
acids,  which  he  named  deutero-  and  trito-catechuic  acids  ;  but  this  view  has  not 
been  confirmed. 

3  Ibid,  clxviii.  111. 

4  Kraut  and  Delden,  ibid,  cxxviii.  285  ;  Malin,  ibid,  cxxxiv.  118. 

5  Barth  and  Pfaundler,  ibid,  cxxvii.  357. 

6  Barth  and  Hlasiwetz,  ibid.  cxxx.  346  ;  cxxxiv.  277  ;  cxxxix.  78. 

7  Malin,  ibid.  clii.  109. 


PROTOCATECHUIC  ACID.  351 

sulphonic  acid,1  bromanisic  acid,  iodoparahydroxybenzoic  acid, 
sulphoparahydroxybenzoic  acid  and  sulphometahydroxybenzoic 
acid,2  is  of  theoretical  interest. 

It  is  best  prepared  from  East  Indian  kino,  which  is  obtained 
by  making  incisions  in  the  bark  of  Pterocarpus  Marsupium  ;  the 
sap  flows  out  and  dries  to  a  dark  red,  transparent  mass,  which  is 
employed  in  medicine  as  an  adhesive,  and  for  many  purposes  as 
a  substitute  for  catechu.  One  part  of  the  finely-powered  kino  is 
then  gradually  brought  into  a  well-stirred  melt  of  three  parts  of 
caustic  soda  kept  at  a  low  temperature.  When  the  mass  has 
become  coloured  a  light  orange  brown,  it  is  dissolved  in  20  parts 
of  water,  and  the  solution  acidified  with  sulphuric  acid,  and 
allowed  to  stand  for  twenty-four  hours.  The  filtrate  is  extracted 
with  ether,  the  latter  evaporated  and  the  residue  repeatedly 
crystallized  from  water.3  The  aqueous  solution  of  the  acid  may 
also  be  precipitated  with  lead  acetate,  the  precipitate  washed 
and  finally  decomposed  by  sulphuretted  hydrogen  (Barth  and 
Hlasiwetz). 

According  to  Eijkman,  protocatechuic  acid  occurs  in  the  fruit 
of  Illicium  religiosum.* 

It  crystallizes  in  monoclinic  needles,  containing  one  molecule  of 
water  which  is  lost  at  100°,  and  melts  at  1940;5  it  dissolves  in 
53—55  parts  of  water  at  14°  and  in  35—37  parts  at  75°— 80°,6 
is  very  soluble  in  alcohol,  less  so  in  ether,  and  almost  insoluble 
in  boiling  benzene.  Its  aqueous  solution  is  coloured  an  intense 
bluish  green  by  ferric  chloride,  the  colour  being  changed  to  dark 
red  by  the  addition  of  sodium  carbonate.  The  solutions  of  its 
salts  are  coloured  violet  by  ferrous  sulphate.  It  reduces  an 
ammoniacal  silver  solution,  but  not  Fehling's  solution ;  on  dry 
distillation,  or  when  heated  to  330° — 350°  with  caustic  soda,  it 
decomposes  into  carbon  dioxide  and  catechol.  When  nitrogen 
trioxide  is  passed  into  its  ethereal  solution,  oxalic  and  dihydroxy- 
tartaric  acids  are  formed  (Part  III.  p.  58),  together  with  smaller 
quantities  of  dinitrophenol,  picric  acid,  dinitrodihydroxyquinone 
and  nitroparahydroxybenzoic  acid.7 

Protocatechuic  acid  is  produced  along  with  benzoic  acid  when 
gum  benzoin  is  fused  with  caustic  potash;  a  compound  of  the 


1  Earth,  Ann.  Chem.  Pharm.  cliv.  364. 

2  Ibid.  clix.  232. 

3  Stenhouse,  ibid,  clxxvii.  188. 

4  Ber.  Deutsch.  Chem.  Ges.  xviii.  Ref.  281. 

5  Barth  and  Schmidt,  ibid.  xii.  1265. 

6  Tiemann  and  Nagai,  ibid.  x.  211. 

7  Gruber,  ibid.  xii.  514. 


352  AROMATIC  COMPOUNDS. 

formula  C7H603  +  C7H604+  2H20  is  formed,  crystallizing  in  short 
prisms,  and  the  two  acids  cannot  be  separated  by  re-crystallization 
or  by  fractional  precipitation  with  lead  acetate.  On  treatment 
with  bromine,  however,  the  parahydroxybenzoic  acid  is  converted 
into  tribromophenol,  while  the  protocatechuic  acid  remains 
unaltered  (Earth  and  Hlasiwetz). 

Barium  protocatechuate,  (C6H3(OH)2C02)2Ba  -f  5H20,  forms 
granular  crystals  ;  when  its  solution  is  treated  with  concentrated 
baryta  water,  the  basic  salt  separates  out  in  warty  crystals,  which, 
after  drying  at  130°,  have  the  formula  (C6H3(02Ba)C02)2Ba.1 

Lead  protocatechuate,  (C(5H3(OH)2C02)Pb  +  2H2O.  An  amor- 
phous precipitate  of  (C6H3(OPb.OH)2CO2)2Pb  is  obtained  by  the 
addition  of  lead  acetate  to  an  aqueous  solution  of  the  acid ;  the 
solution  of  this  in  dilute  acetic  acid  deposits  the  normal  salt  in 
small  crystals. 

Methyl  protocatechuate,  C6H3(OH)2CO2.CH3,  crystallizes  from 
hot  water  in  needles,  which  melt  at  134-5°;  ferric  chloride  colours 
its  aqueous  solution  green.2 

2194  Vanillic  acid,  C6H3(OCH3)(OH)C02H,(CO2H :  OCH3 :  OH 
=  1  :  3  : 4),  was  first  obtained  by  Tiemann  by  the  oxidation  of 
coniferin  with  potassium  permanganate ; 3  it  is  also  formed  by 
the  action  of  air  on  finely  divided,  moist  vanillin,4  and  has  been 
prepared  by  various  other  reactions,  which  will  be  described 
below.  It  crystallizes  in  needles,  melting  at  2070,5  and  sublimes 
without  decomposition;  it  dissolves  in  850  parts  of  water  at  14°, 
and  in  39  parts  at  100°,  is  very  readily  soluble  in  alcohol,  but 
somewhat  le*ss  so  in  ether ;  it  is  not  coloured  by  ferric  chloride, 
and  in  the  pure  state  is  quite  odourless.6  On  heating  with  caustic 
soda  and  chloroform,  vanillin  is  formed  and  only  one  aldehydo- 
vanillic  acid,7  proving  that  the  hydroxyl-group  is  in  the  para- 
position,  since  both  ortho-  and  para-compounds  may  be  formed 
in  this  reaction  (p.  286). 

Methyl  vanillate,  C6H3(OCH3)(OH)C02.CH3,  crystallizes  from 
dilute  alcohol  in  lustrous  needles,  melts  at  62° — 63°,  and  boils 
at  285°— 2870.8 

Vanillic  acid  ghicoside,  or  Glucovanillic  acid,  (C6H3(OCH3) 
OC6HnO5)CO2H  +  H2O,  is  formed,  together  with  glucovanillin,9 

Barth,  Ann.  Chem.  Pharm.  cxlii.  246. 

P.  Meyer,  Bar.  Dcutsch.  Chem.  Ges.  xi.  129. 

Ibid.  viii.  509.  4  Ibid.  viii.  1123. 

Ibid.  ix.  414.  6  Ibid.  x.  60. 

Tiemann  and  Mendelsohn,  ibid.  ix.  1278. 

Matsmoto,  ibid.  xi.  128.  9  Tiemann,  ibid,  xviii.  1595. 


ISOVANILLIC  ACID.  353 


by  the  action  of  potassium  permanganate  on  coniferin,  and 
crystallizes  from  hot  water  in  fine  prisms,  which  lose  their 
water  of  crystallization  at  100°,  and  melt  at  2109— 212°. 
It  is  decomposed  by  emulsin  or  by  boiling  with  dilute  acids 
into  grape  sugar  and  vanillic  acid.1 

Acetylvanillic  acid,  C6H3(OCH3)(OCO.CH3)C02H,  is  formed 
by  heating  vanillic  acid  with  acetic  anhydride,2  and  from 
eugenol  acetate,  C6H3(OCH3)(OC2H30)C3H5,  acetylferulic  acid,3 
C6H3(OCH3)(OC2H3O)C2H2.C02H,  acetylcreosol,*  C6H3(OCH3) 
(OC2H30)CH3  and  acetylhomovanillic  acid5  by  oxidation  with 
potassium  permanganate.  It  crystallizes  from  dilute  alcohol  in 
fine  needles,  which  melt  at  142°,  and  are  decomposed  on  boiling 
with  caustic  potash  into  acetic  and  vanillic  acids. 

Benzoyhanillic  acid,  C6H3(OCH3)(OCO.C6H5)C02H,  is  pre- 
pared by  the  oxidation  of  benzoyleugenol,  and  crystallizes  from 
dilute  alcohol  in  small  plates  which  have  a  peculiar  surface 
lustre,  and  melt  at  1780.6 

Isovanillic  acid,  C6H3(OH)(OCH3)CO2H,  (C02H  :OH:  OCH3 
m  1 :  3  : 4).  Tiemann  found  that  when  dime  thy  Iprotocatechuic 
acid  is  heated  with  dilute  hydrochloric  acid,  vanillic  acid  and 
an  isomeric  methylprotocatechuic  acid  are  formed,7  the  latter 
being,  as  was  proved  by  Beckett  and  Wright,8  identical  with 
an  acid  which  Matthiessen  and  Foster  had  previously  ob- 
tained by  heating  hemipinic  acid,  C6H2(OCH3)2(C02H)2,  with 
hydrochloric  acid.9  According  to  Matsmoto,  who  proposed  the 
name  isovanillic  acid,  it  is  most  readily  prepared  by  heating 
2  parts  of  di methylprotocatechuic  acid  to  160° — 170°  with  a 
mixture  of  25  parts  of  hydrochloric  acid  of  specific  gravity  1'2 
and  50  parts  of  water  for  four  to  five  hours.  The  product 
is  repeatedly  crystallized  from  water  in  order  to  remove  vanillic 
and  protocatechuic  acids  which  are  formed  in  the  reaction,  and 
is  then  freed  from  any  unaltered  dimethylprotocatechuic  acid  by 
conversion  into  the  acetyl  compound,  which  is  then  recrystallized 
and  saponified  by  dilute  caustic  potash.10 

1  Tiemann  and  Reimer,  Ber.  Deutsch.  Chem.  Ges.  viii.  515. 

2  Tiemann  and  Nagai,  ibid.  viii.  1142. 

3  Tiemann,  ibid.  ix.  409. 

4  Tiemann  and  Mendelsohn,  ibid.  x.  57. 

5  Tiemann  and  Nagai,  ibid.x.  201. 

6  Kraaz  and  Tiemann,  ibid.  xv.  2068. 

7  Ibid.  viii.  513. 

8  Journ.  Chcm.  Soc.  1876,  i.  302. 

9  Proc.  Roy.  Soc.  xii.  502. 

10  Bcr.  Deutsch.  Chem.  Gcs.  xi.  125. 


354  AROMATIC  COMPOUNDS. 

Isovanillic  acid  crystallizes  in  lustrous,  transparent  prisms, 
melting  at  250°,  which  dissolve  in  1,700  parts  of  water  at  14°, 
and  in  160  parts  at  100°.  It  is  readily  soluble  in  alcohol  and 
ether ;  it  gives  no  colour  reaction  with  ferric  chloride. 

Acetylisovanillic  acid,  C6H3(OCO.CH3)(OCH3)CO2H,  crystal- 
lizes from  dilute  alcohol  in  scales,  melting  at  206° — 207°. 

2195  Veratric  acid  or  Dimethylprotocatechuic  acid,  C6H3(OCH3)2 
C02H.  In  the  year  1839,  E.  Merck  discovered  veratric  acid, 
C9H10O4,1  in  the  seeds  of  Veratrum  Sdbadilla,  and  W.  Merck 
then  observed  that  it  decomposes  into  carbon  dioxide  and 
veratrol,  C8H10O2,  on  heating  with  caustic  baryta.2  By  the 
oxidation  of  methyleugenol,  Grabe  and  Borgmann  obtained 
bimethoxybenzoic  acid,3  which  was  shown  by  Tiemann  4  and  by 
Erlenmeyer  and  Wassermann 5  to  be  identical  with  the  di- 
methylprotocatechuic  acid  which  Kolle  had  prepared  by 
heating  protocatechuic  acid  with  caustic  potash,  methyl  iodide 
and  wood-spirit ; 6  Korner  then  showed  that  this  compound  is 
also  identical  with  veratric  acid,  veratrol  being  dimethylcate- 
chol.7  Veratric  acid  is  also  formed  when  veratrin  and  pseudo- 
aconitine  are  heated  with  alcoholic  potash.8  In  order  to  prepare 
it,  1  part  of  methyleugenol,  C6H3(OCH3)2C3H5,  is  shaken  up 
with  10 — 15  parts  of  water,  and  a  solution  of  3'5  parts  of  potas- 
sium permanganate  in  20 — 30  parts  of  water  heated  to  80— 90° 
gradually  added.  The  filtrate  is  concentrated  by  evaporation 
and  precipitated  with  hydrochloric  acid.9  Yeratric  acid  dissolves 
in  2,100  parts  of  water  at  14°,  and  in  160  parts  at  100°,  and 
crystallizes  from  a  concentrated  solution  at  a  temperature  above 
50°  in  anhydrous  needles,  while  crystals  containing  a  molecule  of 
water  are  obtained  from  very  dilute  solutions  at  any  temperature 
below  this.  It  melts  at  174° — 175°  and  can  be  sublimed.  It 
dissolves  readily  in  alcohol  and  ether ;  ferric  chloride  produces 
no  colouration. 

Methyl  veratrate,  C6H3(OCH3)2C02.CH3,  is  formed,  together 
with  methyl  protocatechuate  and  methyl  isovanillate,  when 
protocatechuic  acid  is  heated  with  caustic  potash,  methyl  iodide 
and  wood  spirit,10  no  methyl  vanillate  being  formed.11 

I  Ann.  Chem.  Pharm.  xxix.  188.  2  Ibid,  cviii.  60. 

3  Ibid,  clviii.  282.  4  Ber.  Deutsch.  Chem.  Gcs.  viii.  514. 

5  Ann.  Chem.  Pharm.  clxxix.  366.  6  Ibid.  clix.  240. 

f  Ber.  Deutsch.  Chem.  Gcs.  ix.  582. 

8  Wright  and  Luff,  Journ.  Chem.  Soc.  1878,  i.  160  and  352. 

9  Tiemann  and  Matsmoto,  Ber.  Deutsch.  Chem.  Ges.  ix.  937. 
10  Matsmoto,  ibid.  xi.  122. 

II  Tiemann,  Ber.  Deutsch.  Chem  Ges.  viii.  513. 


PIPERONIC  ACID.  355 


The  ether  is  obtained  pure  when  a  solution  of  the  acid  in 
anhydrous  methyl  alcohol  is  saturated  with  hydrochloric  acid, 
or  when  vanillic  acid  is  heated  with  caustic  potash  and  methyl 
iodide.  It  crystallizes  in  odourless  needles,  melts  at  59° — 60° 
and  boils  at  about  300°  (Matsmoto). 

Melting-  Boiling- 

point,  point. 

Ethyl  veratrate,1 

C6H3(OCH3)2C02.C2H5 43°— 44°     295°— 296° 

Ethylvanillic  acid,2 

C6H3(OC2H5)(OCH3)C02H   .    .    .  193°— 194° 
Diethylprotocatechuic  acid,3 

C6H3(OC2H5)2C02H,     .    .    .    .    .         149° 

Piper onic  acid,  C6H3(O2CH2)C02H,  was  prepared  by  Fittig 
and  Mielk  by  the  oxidation  of  piperic  acid  or  piperonal  with 
potassium  permanganate,4  while  Fittig  and  Remsen  obtained  it 
by  heating  protocatechuic  acid  with  caustic  potash  and  methy- 
lene  iodide  : 5 

/OK  \CH2 

C6H  /  OK        +  CH2I2  =  C6H3--  O  /  +  2KI. 

\C02K  \C02K 


It  occurs  in  small  quantity  in  Paracoto  bark,  which  is  collected 
on  the  river  Mapiri  in  Bolivia,  and  has  been  detected  in  true 
Goto  bark,  which  is  also  found  in  Bolivia.6 

Piperonic  acid  is  scarcely  soluble  in  cold  water,  slightly  in 
boiling  water,  from  which  it  separates  in  small  needles,  or,  on 
very  gradual  cooling,  in  characteristic  crystals,  which  resemble 
in  appearance  small  twisted  threads  of  sewing  cotton.  It  is  also 
slightly  soluble  in  ether  and  cold  alcohol,  separating  from  a 
hot  alcoholic  solution  in  larger  crystals.  It  is  obtained  in  the 
purest  state  by  sublimation,  which  yields  large,  compact,  glitter- 
ing prisms  with  acute  terminal  planes ;  it  melts  at  227*5° — 
228'5°,  but  sublimes  at  a  lower  temperature. 

When  it  is  heated  with  phosphorus  pentachloride,  a  liquid 
chloride  is  formed  which  yields  a  chlorinated  acid  on  decom- 
position with  cold  water ;  this  substance  is  probably  a  dichloro- 
piperonic  acid  and  is  resolved  on  heating  with  water  into 

1  Tiemann  and  Matsmoto,  Ber.  Dcutsch.  Chcm.  Ges.  ix.  942. 

2  Tiemann,  ibid.  viii.  1130  ;  Wassermann,  Ann.  Chem.  Pharm.  clxxix.  379. 

3  Kolle,  ibid,  clix.'  245.  4  Kolle,  ibid.  clii.  40. 

8  Ibid,  clxviii.  93.  6  Hesse  and  Jobst,  ibid,  cxcix.  63. 


356  AROMATIC  COMPOUNDS. 

hydrochloric  acid,  carbon  dioxide  and  protocatechuic  acid. 
Piperonic  acid  is  decomposed  by  dilute  hydrochloric  acid  at 
170°,  or  by  water  at  210°,  into  carbon  dioxide  and  protocatechuic 
acid,  so  that  it  behaves  in  an  analogous  manner  to  its  aldehyde 1 
(p.  347).  _ 

Potassium  piperonate,  C8H5O4K  +  H2O,  crystallizes  in  long 
needles,  which  are  readily  soluble  in  water. 

Calcium  piperonate,  (C8H504)2Ca  +  3H20,  is  slightly  soluble 
in  cold,  readily  in  hot  water,  and  crystallizes  in  fascicular  groups 
of  needles  or  plates. 

Silver  piperonate,  C8H5O4Ag,  is  a  granular  precipitate,  which 
crystallizes  from  hot  water  in  large,  narrow  plates. 

Ethyl  piperonate,  C8H5O4.C2H5,  is  a  mobile,  strongly  refractive 
liquid,  which  has  a  pleasant  fruity  odour  (Jobst  and  Hesse). 

Ethyleneprotocatechuic  acid,  C6H3(O2C2H4)C02H,  is  formed  by 
heating  protocatechuic  acid  with  caustic  potash  and  ethylene 
bromide.2  It  is  slightly  soluble  in  cold  water  and  crystallizes 
from  a  boiling  solution  in  splendid,  broad,  lustrous  needles.  It 
dissolves  in  almost  every  proportion  in  alcohol,  from  which  it 
separates  on  dilution  in  druses  composed  of  short,  lustrous 
prisms,  which  melt  at  133'5°,  and  sublime  in  lustrous  prisms 
when  carefully  heated. 

The  calcium  salt,  (C9H7O4)2Ca  + 2H2O,  crystallizes  from  hot 
water  in  well-developed,  compact,  monoclinic  prisms. 

Bromoprotocateckuic  acid,  C6H2Br(OH)2CO2H,  is  prepared  by 
triturating  protocatechuic  acid  with  bromine ;  it  crystallizes 
from  hot  water  in  fine,  rhombic  needles,  and  is  converted  into 
gallic  acid  by  fusion  with  potash.8 

2196  Maclurin,  C13H10O6  +  H20,  occurs  in  fustic  (Morus,s.  Ma- 
dura tinctoria),  and  was  described  by  Wagner  as  morintannic 
acid.4"  Its  correct  formula  has  been  determined  by  Hlasiwetz 
and  Pfaundler.5  According  to  Wagner,  the  dirty  yellow,  crys- 
talline masses  found  in  the  centre  of  the  logs  consist  almost 
entirely  of  impure  maclurin,  which  can  readily  be  purified 
by  repeated  crystallization  from  slightly  acidified  water.  Bene- 
dikt  employs  as  his  raw  material  the  muddy  deposit  which 
is  obtained  as  a  by-product  in  the  manufacture  of  fustic 
extract,  and  which  consists  of  maclurin  and  its  calcium 

1  Fittig  and  Remsen,  Ann.  Chem.  Pharm.  clix.  129. 

2  Fittig  and  Macalpine,  ibid,  clxviii.  99. 

3  Barth,  ibid,  cxlii.  246  ;  Ber.  Dcutsch.  Chem.  Gcs.  viii.  1484. 

4  Journ.  Prakt.  Chem.  li.  82  ;  Hi.  449. 

5  Ann.  Chem.  Pharm.  cxxvii.  352. 


MACLURIN  AND  LUTEOLIN.  357 

salt.  It  is  ground  up  with  dilute  hydrochloric  acid  pressed,  and 
repeatedly  crystallized  from  hot  water.  In  order  to  remove  any 
adhering  colouring  matter,  it  is  dissolved  in  water  and  treated 
with  lead  acetate.  A  current  of  sulphuretted  hydrogen  is  then 
passed  through  the  hot  liquid,  which  is  subsequently  filtered  and 
allowed  to  cool  ;  the  pure  maclurin  is  thus  obtained  as  a  light 
yellow,  crystalline  powder.  It  becomes  anhydrous  at  130°,  and 
melts  at  200°.  On  boiling  with  water  and  barium  carbonate 
one  molecule  of  carbon  dioxide  is  evolved  for  every  two 
molecules  of  maclurin  present  (Benedikt),  while  the  salt 
C13H8PbO6  +  H2O  is  deposited  in  yellow  plates  when  lead 
acetate  is,  added  to  the  boiling  solution  (Hlasiwetz  and 
Pfaundler). 

When  maclurin  is  boiled  with  concentrated  caustic  potash  solu- 
tion or  heated  to  120°  with  dilute  sulphuric  acid,  it  decomposes 
smoothly  into  protocatechuic  acid  and  phloroglucinol. 

Benedikt  therefore  proposes  the  following  formulae  for  maclurin 
and  its  lead  salt  :  1 

OH  /OH 


co. 

Luteolin,  C20H1408,  was  discovered  by  Chevreul  in  weld 
la  lutea),2  and  analyzed  by  Moldenhauer,3  who  obtained 
lumbers  which  led  to  the  formula  given  above,  while  Paraf 

id  Schiitzenberger  calculated  the  composition  2C12H8O5-|-3H2O 
from  the  results  of  their  investigation  and  somewhat  unsatis- 
factory analyses.4  It  is  obtained  by  extracting  the  dried  plant 
with  water  containing  5  —  6  per  cent,  of  alcohol,  concentrating 
the  filtrate  by  evaporation  and  purifying  the  crude  luteolin  thus 
obtained  by  recrystallization  from  alcohol  or  a  mixture  of  water 
and  glycerol. 

It  crystallizes  in  small,  yellow  needles,  which  dissolve  in 
14,000  parts  of  cold  water,  in  5,000  parts  at  100°  and  in  37 
parts  of  alcohol.  It  readily  forms  a  deep  yellow  solution  in 
alkalis,  and  dissolves  in  cold  sulphuric  acid  forming  a  reddish 
yellow  solution  from  which  it  is  precipitated  by  water.  A  small 

1  Ann.  Chem.  Pharm.  clxxx.  114.  2  Berzelius,  Jahresb.  xi.  280. 

3  Ann.  Chem.  Pharm.  c.  180.  4  Compt.  Rend.  lii.  92. 

254 


358  AROMATIC  COMPOUNDS. 

quantity  of  ferric  chloride  produces  a  green  colouration,  which 
passes  into  brownish  red  on  the  addition  of  more  of  the  reagent. 
Its  hot  aqueous  solution  dyes  wool,  mordanted  with  alum,  a 
beautiful  daffodil-yellow  (Chevreul).  On  fusion  with  potash  it 
is  decomposed  with  evolution  of  hydrogen  into  phloroglucinol 
and  protocatechuic  acid  :  1 

CHO  +  3H)  =  2CH0  +  CH0  +  H 


MMg  764        663         2. 

Rochleder  states,  however,  that  the  amount  of  phloroglucinol 
formed  is  much  greater  than  corresponds  to  this  equation.  The 
formula  of  luteolin  is  by  no  means  accurately  determined  and 
its  constitution  is  quite  unknown. 


SYMMETRIC    METADIHYDROXYBENZOIC    ACID 
OR  a-RESORCYLIC  ACID  (1:3:  5). 

2197  This  substance  is  obtained  by  fusing  /3-disulphobenzoic 
acid,2  metabromosulphobenzoic  acid  and  parabromosulphobenzoic 
acid  3  with  caustic  potash.  It  crystallizes  with  one  and  a  half 
molecules  of  water  in  needles  or  prisms,  which  melt  at  232°— 
233°,  are  tolerably  soluble  in  cold,  ^ readily  in  hot  water, 
alcohol  and  ether,  and  give  no  colouration  with  ferric  chloride. 
On  fusion  with  caustic  soda  it  decomposes  above  300°  into 
resorcinol  and  carbon  dioxide.4  A  very  characteristic  reaction 
is  that  when  heated  with  4  parts  of  sulphuric  acid  to  140°,  a 
deep  red  solution  is  formed  from  which  water  precipitates  green 
flocks  of  anthrachrysone,  C14H4(OH)402,  which  is  a  derivative  of 
anthracene,  and  is  also  formed  by  the  dry  distillation  of  the 
acid.  Lead  acetate  does  not  produce  a  precipitate  when  added 
to  an  aqueous  solution  of  the  acid. 

Ethyl  a-resorcylate,  C6H3(OH)2CO2.C2H5,  crystallizes  from 
water  in  long  prisms  which  melt  below  100°. 

Dimethyl-a-resorcylic  acid,  C6H3(OCH3)2CO2H,  is  formed  when 
a-resorcylic  acid  is  heated  with  caustic  potash,  methyl  iodide  and 
wood-spirit,  and  when  dimethylorcinol  is  oxidized  with  potassium 

1  Rochleder,  Journ.  Prakt.  Chcm.  xcix.  433. 

2  Earth  and  Senhofer,  Ann.  Chcm.  Pharm.  clix.  217. 
8  Bottinger,  Bcr.  Deutech.  Chem.  Ges.  viii.  374. 

4  Barth  and  Schreder,  ibid.  xii.  1258. 


RESORCYLIC  ACIDS.  359 

permanganate.1     It  crystallizes  from  hot  water  in  fine  needles, 
which  melt  at  175°— 176°. 

Diethyl-a-resorcylic   acid,  C6H3(OC2H5)2CO2H,  was   prepared 
by  Earth  and  Senhofer  from  the  acid  by  the  action  of  ethyl 
iodide.2     It  forms  elongated  prisms,  which  melt  at  87° — 88°,  and 
are  decomposed  by  distillation  with  lime  into  carbon  dioxide  and,,, 
diethylresorcinol.3 

a-Bromoresorcylic  acid,  G6H2Br(OH)2C02H,  is  formed  by  the 
action  of  bromine  water  on  an  aqueous  solution  of  a-resorcylic 
acid,  and  crystallizes  from  hot  water  in  long  needles,  which  melt  at 
253°,  and  give  a  yellowish  brown  colouration  with  ferric  chloride. 
It  gives  the  same  reaction  with  sulphuric  acid  as  a-resorcylic 
acid,  and  is  converted  into  gallic  acid  by  fusion  with  caustic 
potash  (Barth  and  Senhofer). 


ASYMMETRIC   METADIHYDROXYBENZOIC 
ACID  OR  ^-RESORCYLIC  ACID,  (1:2:4). 

2198  This  acid  is  formed  when  paracresolsulphonic  acid,4  and 
a-disulphobenzoic  acid 5  are  fused  with  caustic  potash,  and  may 
also  be  obtained,  together  with  a  large  amount  of  resorcinol, 
when  its  aldehyde  is  fused  for  a  short  time  with  caustic  potash.6 
It  may  also  be  prepared,  together  with  7-resorcylic  acid  and 
dihydroxyphthalic  acid,  C0H2(OH)2(C02H)2,  by  heating  1  part 
of  resorcinol  with  4  parts  of  ammonium  carbonate  and  5  parts 
of  water  to  120° — 1300,7  and  still  more  readily  by  heating 
resorcinol  in  an  open  flask  with  a  concentrated  solution  of 
potassium  bicarbonate.  It  is  very  slightly  soluble  in  cold  water, 
and  crystallizes  from  a  hot  solution  in  needles  containing  one 
and  a  half  molecules  of  water,  one  of  which  is  lost  on  exposure 
to  the  air  (Fahlberg).  It  melts  at  204°— 206°,  and  simultane- 
ously decomposes  into  carbon  dioxide  and  resorcinol.  Its 

1  Tiemann  and  Streng,  Ber.  Deutsch.  Chem.  Ges.  xiv.  2002. 

2  Ann.  Chem.  Pharm.  clxiv.  121. 

3  Barth,  Ber.  Deutsch.  Chem.  Ges.  xi.  1569. 

4  Ascher,  Ann.  Chem.  Pharm.  clxiv.  11. 

8  Blomstrand,  Ber.  Deutsch.  Chem.  Ges.  v.  1088  ;  Fahlberg,  Amer.  Chem,.  Journ. 
ii.  196. 

8  Tiemann  and  Reimer,  Ber.  Deutsch.  Chem.  Ges.  xii.  997  ;  Tiemann  and 
Parrisius,  ibid.  xiii.  2358. 

7  Brunner  and  Senhofer,  ibid.  xiii.  2356  ;  Ber.  Wien.  AJcad.  1879,  ii  504. 


360  AROMATIC  COMPOUNDS. 

solution  is  coloured  dark  red  by  ferric  chloride,  and  does  not 
give  a  precipitate  with  lead  acetate. 

Orthor)iethyl-@-resorcylic  acid,  C6H3(OH)(OCH3)C02H(OCH3 : 
OH  =  2  :  4),  is  formed  when  the  acetyl-derivative  of  its  aldehyde 
is  oxidized  with  potassium  permanganate  and  the  product 
decomposed  by  caustic  potash.  It  is  tolerably  soluble  in  water, 
does  not  crystallize  well,  and  gives  no  colouration  with  ferric 
chloride.1 

Paramethyl-0-resorcylic  acid,  (OH  :  OCH3=2  :  4).  The  methyl 
ether  is  prepared  by  adding  sodium  to  a  solution  of  /3-resorcylic 
acid  in  wood-spirit  and  then  heating  with  methyl  iodide,  the 
acid  being  obtained  from  this  by  boiling  with  caustic  potash 
(Tiemann  and  Parrisius) ;  it  is  also  formed  when  sodium  rnethyl- 
resorcinol  is  heated  to  215°  in  a  current  of  carbon  dioxide  :  2 

C6H4(OCH3)ONa  +  CO2  =  C6H3(OCH3)(OH)CO2Na. 

It  crystallizes  from  hot  water  in  lustrous  needles,  which  melt 
at  151'5°,  and  decompose  into  methylresorcinol  and  carbon 
dioxide  when  rapidly  heated.  Its  aqueous  solution  is  coloured 
an  intense  reddish  violet  by  ferric  chloride. 

Dimethyl- ft-resorcy  lie  acid,  C6H3(OCH,)2CO2H,  is  not  readily 
formed  by  the  further  methylation  of  the  preceding  compound, 
but  may  be  obtained  by  the  oxidation  of  its  aldehyde  with 
potassium  permanganate ;  it  crystallizes  from  hot  water  in  fine 
needles,  melting  at  108°  (Tiemann  and  Parrisius). 

Diethyl-@-resorcylic  acid,  C6H3(()C2H5)2C02H,  was  prepared  in 
a  similar  manner ;  it  forms  needles  which  melt  at  99°.3 


ADJACENT    METADIHYDROXYBENZOIC    ACID 
OR  7-RESORCYLIC  ACID  (1:2:6). 

2199  The  formation  of  this  acid  has  already  been  mentioned  ; 
it  is  very  soluble  in  water,  and  crystallizes  in  fine,  fascicular 
needles,  which  contain  one  molecule  of  water  and  commence  to 
fuse  at  140°,  a  partial  decomposition  into  resorcinol  and  carbon 
dioxide  occurring,  which  becomes  complete  at  a  higher  tempera- 

1  Tiemann  and  Parrisius,  Bcr.  JDewtsch.  Chem.  Ges.  xiii.  2375. 

2  Korner  and  Bertoni,  ibid.  xiv.  847. 

3  Tiemann  and  Lewy,  ibid.  x.  2215. 


HYDROXYSALICYLIC  ACID.  361 

ture.  Its  aqueous  solution  is  coloured  a  deep  bluish  violet  by 
ferric  chloride. 

ry-BromoTesorcylic  acid,  C6H2Br(OH)2C02H  +  H2O,  is  formed 
by  the  action  of  bromine  on  an  ethereal  solution  of  the  acid.  It 
is  slightly  soluble  in  cold  water,  readily  in  alcohol,  and  crystallizes 
in  fine  prisms,  which  lose  their  water  at  100°  and  melt  at 
184°  with  decomposition.  It  is  coloured  violet  by  ferric 
chloride. 

Dimethyl->y-resorcylic  acid,  C6H3(OCH3)2C02H.  When  meta- 
dinitrobenzene  is  treated  with  methyl  alcohol  and  potassium 
cyanide,  methoxynitro^enzonitril)CQH.3(l^O2)(OCH3)C^, is  formed; 
it  crystallizes  from  chloroform  in  pliant  needles,  which  melt  at 
171°,  and  are  converted  on  heating  with  methyl  alcohol  and 
caustic  potash  into  dimethoxylenzonitril,  C6H3(OCH3)2CN,  which 
crystallizes  from  alcohol  in  needles  or  rectangular  tablets, 
melting  at  118°.  It  boils  at  about  310°,  and  when  heated  with 
baryta  water  yields  dimethyl-7-resorcylic  acid,  which  forms 
crystals  melting  at  179°,  and  is  converted  into  7-resorcylic  acid 
by  heating  with  caustic  potash. 

If  methoxynitrobenzonitril  is  heated  with  caustic  potash  and 
ethyl  alcohol,  ethoxymetlioxylienzonitril,  C6H3(OCH3)(OC2H5) 
ON,  is  formed,  and  crystallizes  from  alcohol  in  prisms  or  tablets, 
melting  at  66°.  This  compound  is  also  formed  when  meta- 
dinitrobenzene  is  treated  with  ethyl  alcohol  and  potassium 
cyanide,  and  the  ethoxynitrobenzwiitril,  C6H3(NO<,)(OC2H5)CN, 
thus  formed,  which  melts  at  137°,  is  heated  with  methyl  alcohol 
and  caustic  potash.  A  new  and  simple  proof  is  thus  afforded 
of  the  identity  of  the  positions  1  and  6  in  the  benzene  nucleus.1 


'  HYDROXYSALICYLIC  ACID  OR  PARADIHY- 
DROXYBENZOIC  ACID  (1:2:  5). 

22  oo  This  isomeride  has  been  prepared  by  fusing  iodosalicylic 
acid  with  caustic  potash ; 2  it  is  more  readily  obtained,  however, 
by  fusing  bromosalicylic  acid  with  caustic  soda,3  and  is  also 

1  Lobry  de  Bruyn,  Ber.  Deutsch.  Chem.  Ges.  xviii.  Kef.  148  ;  Chem.  CentralU. 
1884,  119;  1885,  357. 

2  Lautemann,  Ann.  Chcm.  Pharm.  cxx.  311  ;  Liechti,  ibid.  Suppl.  vii.  144; 
Demole,  Ber,  Deutsch.  Chem.  Ges.  vii.  1438  ;  Goldberg,  Jvurn.  Prakt.  Chem.  [2] 
xix.  371. 

3  Leppert  and  Rakowski,  Ber.  Deutsch.  Chem.  Ges.  viii.  788. 


AROMATIC  COMPOUNDS. 


formed  by  the  action  of  nitrous  acid  on  a-amidosalicylic  acid,1 
and  when  quinol  is  heated  with  potassium  bicarbonate,  water 
and  a  little  potassium  sulphite.2  Hlasiwetz  and  Habermann,  by 
fusing  gentisin,  C14H1005,  from  Gentidna  lutea,  with  caustic 
potash,  obtained  a  dihydroxybenzoic  acid,  which  they  named 
gentisic  acid,  since  they  believed  that  it  was  different  from 
those  previously  known;3  they  subsequently  found,  however, 
that  it  is  identical  with  hydroxysalicylic  acid.4  It  is  readily 
soluble  in  water,  alcohol  and  ether,  crystallizes  in  needles  or 
prisms,  which  melt  at  196° — 197°,  and  gives  a  deep  blue  coloura- 
tion with  ferric  chloride.  It  reduces  Fehling's  solution  and 
ammoniacal  silver  solution  on  heating.  On  dry  distillation  it 
is  resolved  into  carbon  dioxide  and  quinol. 

Ethyl  hydroxysalicylate,  C6HS(OH)2C02.C2H5,  crystallizes  from 
hot  water  in  needles,  which  have  a  pleasant  fruity  odour  and 
melt  at  75°  (Goldberg). 

Methylhydroxysalicylic  acid,  C6H3(OCH3)(OH)CO2H.(C02H 
:  OH  :  OCH3=1  :  3  :  5),  was  prepared  by  Korner  and  Bertoni 
by  the  action  of  carbon  dioxide  on  sodium  methylquinol 
at  220° — 2250,5  and  named  a-methylhydroquinoneformic  acid. 
Tiemann  and  Miiller  then  obtained  it  by  oxidizing  the  acetyl- 
derivative  of  the  corresponding  aldehyde  with  potassium  per- 
manganate and  saponifying  the  product  with  caustic  soda.6  It 
crystallizes  from  hot  water  in  long  needles,  melting  at  142°,  and 
gives  a  light  blue  colouration  with  ferric  chloride. 

Dimethylhydroxysalicylic  acid,  C6H3(OCH3)2C02H,  is  formed 
by  the  oxidation  of  its  aldehyde ;  it  crystallizes  from  hot  water 
in  silky  needles,  melting  at  76°.7 

When  the  reactions  of  the  bodies  just  described  are  compared, 
it  is  found  that  protocatechuic  acid,  its  aldehyde,  and  also 
catechol,  which  contain  the  hydroxyls  in  the  ortho-position, 
give  a  green  colouration  with  ferric  chloride.  Those  cofa- 
pounds,  on  the  other  hand,  in  which  a  hydroxyl  is  situated  in 
the  ortho-position  with  regard  to  a  carboxyl,  and  which  can 
therefore  be  considered  as  derivatives  of  salicylic  acid,  give  a 
blue  to  dark  red  colouration,  while  those  in  which  the  hydroxyls 
are  in  the  meta-position,  give  as  little  colouration  as  meta- 
hydroxybenzoic  acid. 

1  Goldberg,  loc.  cit. 

"  Senhofer  and  Sarlay,  Monatsh.  Chem.  ii.  448. 

3  Ann.  GJiem.  Pharm.  clxxv.  66. 

4  Ibid,  clxxx.  343.  6  Ber.  Deutsch.  Chem.  Ges.  xiv.  848. 
6  Ibid.  xiv.  1997.  7  Ibid.  1993. 


GALLIC  ACID. 


According  to  theory,  six  dihydroxybenzoic  acids  can  exist. 
In  addition  to  the  five  just  mentioned,  two  others  have  been 
shortly  described.  One  of  these  was  obtained  by  Leeds  by 
allowing  toluene  saturated  with  nitrogen  peroxide  to  stand  in  a 
loosely  covered  vessel  for  a  whole  summer.  It  crystallizes  from 
alcohol  in  small  plates,  which  sublime  at  170°  without  fusing 
and  give  no  colouration  with  ferric  chloride.1 

Aescioxalic  acid,  C7H6O4,  is  the  name  given  by  Rochleder  to  a 
compound  which  he  obtained,  together  with  formic  acid,  oxalic 
acid  and  frequently  protocatechuic  acid,  by  boiling  aesculetin, 
C9H604,  with  concentrated  caustic  potash  or  baryta  water.  It 
forms  an  extremely  fine  crystalline  mass  and  gives  a  reddish 
brown  colouration  with  ferric  chloride,  which  is  changed  by 
sodium  carbonate  to  purple-violet,  while  ferrous  sulphate  and  a 
little  carbonate  of  soda  produce  an  intense  blue  colouration.2 


TRIHYDROXYBENZOIC  ACIDS,  C6H2(OH)3C02H. 
GALLIC  ACID. 

2201  The  history  of  this  substance  goes  hand  in  hand  with 
that  of  tannic  acid.  In  the  introduction  to  organic  chemistry  it 
has  already  been  mentioned  how  Pliny  states  that  paper  dipped 
in  an  extract  of  nut-galls  was  used  to  ascertain  whether 
verdigris  was  adulterated  with  green  vitriol.  He  also  informs 
us  that  the  juice  of  nut-galls  was  used  to  recognize  a  kind  of 
alumen,  employed  for  dyeing  wool  black,  which  was  either 
natural  green  vitriol  or  a  mineral  containing  this  salt. 

It  was  also  known  in  very  early  times  that  certain  parts  of 
plants,  which  have  an  astringent  taste,  give  a  black  colouration 
with  bodies  containing  iron.  In  addition  to  nut-galls,  Paracelsus 
enumerates  the  sap  of  oaks,  alders,  &c.,  which  colour  solutions  of 
iron  and  copper  black,  and  Libavius  used  this  reaction  in  the 
analysis  of  mineral  waters,  which  were  coloured  black  in  the 
presence  of  iron,  but  only  darkened  when  containing  copper  ;  he 
thus  discovered  the  presence  of  copper  vitriol  in  the  "  Wein- 
brunnen  "  at  Schwalbach. 

Tachenius  states  in  Hippocrates  chymicus,  1766,  that  tinc- 
ture of  nut-galls  produces  various  coloured  precipitates  with 

1  Ber.  Deutsch.  Chcm.  Ges.  xiv.  482.  2  Jahresb.  CJiem.  1867,  752. 


AROMATIC  COMPOUNDS. 


solutions  of  iron,  copper,  lead  and  mercury,  and  separates 
metallic  gold  from  solutions  of  its  salts.  Other  astringent 
plants  have  a  similar  action,  which  he  compares  with  that 
of  the  volatile  alkalis,  since  these  remove  acids  from  vitriols 
in  a  similar  manner.  Lemery  takes  the  same  view  in  his 
paper  on  the  kinds  of  vitriol  and  the  formation  of  ink,  which 
is  published  in  the  Memoirs  of  the  Paris  Academy  for  1707 ; 
nut-galls,  according  to  him,  are  of  an  absorbent  or  alkaline 
nature,  and  therefore  act  like  salt  of  tartar,  lime-water,  ammonia, 
&c.  That  the  latter  do  not  produce  a  black  precipitate  with 
iron  is  accounted  for  by  the  fact  that  the  sulphurous  particles 
present  in  nut-galls  are  absent  in  the  alkalis.  As  a  proof  of 
this  he  mentions  that  when  these  absorbent  substances  are  made 
to  combine  with  sulphur,  they  do  give  a  black  precipitate  with 
solutions  containing  iron. 

Bergman,  on  the  other  hand,  suggested  in  1775,  that  a 
vegetable  acid  is  contained  in  astringent  substances,  and  in 
his  Elemens  de  Chymie  1777,  published  by  Morveau,  Maret,  and 
Durande,  it  is  stated  that  on  the  dry  distillation  of  nut-galls  a 
substance  sublimes  which  blackens  solutions  of  iron  and  behaves 
as  a  true  acid.  In  order  to  obtain  it  in  a  purer  condition, 
Retzius,  in  1783,  treated  the  dried  extract  of  nut-galls  with 
cold  water,  and  in  this  way  obtained  a  substance  which  had  the 
properties  of  an  acid  and  effervesced  with  alkaline  carbonates. 
In  1786,  Scheele  prepared  gallic  acid  by  exposing  extract  of  nut- 
galls  to  the  air  in  a  warm  place  and  frequently  removing  the 
film  of  mould  which  was  formed.  The  crystalline  precipitate 
which  gradually  separated  out  was  purified  by  recrystallization. 
He  observed  that  when  gallic  acid  is  heated  a  body  sublimes 
which  also  precipitates  iron  salts,  but  which  he  considered  to  be 
different  from  gallic  acid,  a  view  which  was  also  taken  by 
Berthollet  in  his  Statique  chimique,  1803,  while  Fourcroy  and 
Berzelius  believed  that  the  sublimate  is  the  pure  gallic  acid,  this 
being  denied  by  Braconnot  and  also  by  Pelouze  (Part  III.,  p. 
181).  The  astringent  constituent  of  nut-galls,  subsequently 
called  tannic  acid,  was  first  recognized  as  a  distinct  substance 
by  Deyeux  in  1793,  and  more  definitely  by  Seguin  in  1795, 
after  which  Berzelius  obtained  it  in  a  pure  or  almost  pure  con- 
dition. It  had  already  been  noticed  that  it  is  readily  converted 
into  gallic  acid,  but  the  relations  of  the  two  substances  had  not 
been  explained,  although  many  chemists  had  investigated  the 
question. 


GALLIC  AND  TANNIC  ACIDS.  365 

Pelouze  and  Berzelius  gave  to  tannic  acid  the  formula 
C18H18O12,  which  was  altered  by  Liebig  to  C18H16O12,  since  the 
latter  explains  in  a  simple  manner  its  conversion  into  gallic 
acid  in  presence  of  water  and  oxygen  :  "  From  one  atom  of 
tannic  acid  and  four  atoms  of  oxygen,  exactly  two  atoms  of 
gallic  acid  and  two  atoms  of  carbonic  acid  are  formed,  while 
according  to  the  formula  C18H18O12,  two  atoms  of  hydrogen 
remain  over,  and  no  one  knows  what  becomes  of  them." l  At 
a  later  period  he  proposed  the  formula  C18H10O9  4-  3aq,  which 
can  be  expressed  as  the  sum  of  the  formulas  of  anhydrous 
acetic  acid  and  gallic  acid ;  he  had  found  that  tannic  acid  can 
be  converted  into  gallic  acid  without  the  intervention  of  oxygen 
by  simply  boiling  for  a  few  minutes  with  caustic  potash,  or 
better,  dilute  sulphuric  acid.2  He  could  not,  however,  detect 
any  acetic  acid  and  suggested  that  an  isomeride  of  this  is 
formed,  which,  however,  from  the  behaviour  of  tannic  acid 
towards  sulphuric  acid,  could  not  be  a  sugar 3  as  had  been 
suggested  by  Stas.4 

Wetherill,  on  the  other  hand,  assumed  that  tannic  and  gallic 
acids  were  isomeric,5  while  Mulder  gave  to  the  former  the 
formula  C14H10O9,  according  to  which  it  forms  two  molecules  of 
gallic  acid  by  the  assumption  of  the  elements  of  water ; 6 
subsequently,  however,  he  altered  his  formula  to  C14H12O9,  and 
looked  upon  gallic  acid  as  an  oxidation  product.7 

Tannic  acid  was  then  carefully  investigated  in  Liebig's 
laboratory  by  Strecker,  who  succeeded  in  resolving  it  into  grape 
sugar  and  gallic  acid,  expressing  the  reaction  by  the  following 
equation  : 8 

C^Ar  +  4H20  =  3C7H605  +  C6H12O6. 

This  view  was  almost  universally  accepted,  the  .more  so  as 
other  tannic  matters  had  proved  to  be  glucosides,  and  as 
the  formation  of  gallic  acid  by  fermentation  received  a  simple 
explanation.  According  to  Strecker's  equation,  29 '1  per  cent, 
of  grape  sugar  should  be  formed,  while  he  only  obtained  15 — 22 
per  cent.,  and  Rochleder  found  that  by  proper  purification  the 
amount  can  be  reduced  to  4  per  cent,  without  altering  the 
chemical  and  physical  properties  of  the  tannic  acid  to  any 

1  Ann.  Chem.  Pharm.  x.  172.  2  Ibid.  xxvi.  128. 

3  Handb.  Chem.  854.  *  Ann.  Chem.  Pharm.  xxx.  205. 

3  Journ.  PraJct.  Chem.  xlii.  247.  6  Jahrcsb.  Chem.  1848,  524. 

7  Ibid.  1858,  261.  8  Ann.  Chem.  Pharm.  xc.  328. 


366  AROMATIC  COMPOUNDS. 

important  extent.1  His  results  confirmed  those  of  Knop,  who 
succeeded  in  converting  95  per  cent,  of  the  tannic  acid  into 
gallic  acid,  ellagic  acid,  C14H6O8,  and  a  carbohydrate  being  also 
formed.2  Stenhouse  had  previously  arrived  at  similar  results, 
having  found  that  by  the .  use  of  sufficiently  dilute  sulphuric 
or  hydrochloric  acid  almost  the  whole  of  the  tannic  acid  can  be 
converted  into  gallic  acid.3 

Rochleder  then  assumed  that  the  sugar  is  formed  from  some 
admixture,  and  that  tannic  acid  stands  in  the  same  relation  to 
gallic  acid  as  dextrin  to  grape  sugar.  Hlasiwetz  remarks  on 
this  question  :  "  If  tannin  is  not  a  glucoside,  it  may  perhaps  be 
a  digallic  acid,  which  corresponds  to  gallic  acid  in  the  same  way 
as  diethylene  alcohol  to  ordinary  glycol,  and  it  would  then  have 
the  formula  which  was  first  proposed  for  it  by  Mulder  : 

2C7H606-H20  =  C14H1009. 

"  The  analyses  of  tannin  and  its  salts  agree  with  this  com- 
position as  well  as  can  be  expected  in  the  case  of  a  substance 
which  is  so  difficult  to  purify."  4 

Lowe,  however,  came  to  a  different  conclusion ;  he  found  that 
silver  nitrate  and  arsenic  acid  are  reduced  by  gallic  acid  with 
formation  of  ellagic  acid  and  a  substance  which  has  all  the  pro- 
perties of  tannic  acid,  so  that  he  considered  the  latter  to  be  an 
oxidation  product  of  gallic  acid.5  He  subsequently  found  that 
the  correct  formula  of  tannic  acid  is  C14H10O9,  but  assumed  that 
gallic  acid  is  not  formed  from  it  only  by  assumption  of  water, 
but  that  a  molecular  change  takes  place.6 

Schiff,  on  the  contrary,  showed  conclusively  that  arsenic  acid 
and  also  phosphorus  oxychloride  simply  exert  a  dehydrating 
action,  and  that  the  digallic  acid  thus  formed  is  identical  with 
tannic  acid.  This  question  will  be  more  fully  considered  under 
the  latter. 

2202  Gallic  acid  occurs  ready  formed  in  nut-galls,  sumach  and 
divi-divi,  the  fruit  of  Caesalpinia  coriaria.7  It  is  also  found  in  the 
leaves  of  the  red  bear-berry  (ArctostapTiylos  Uva  ursi),8  in  China 
tea,9  and  in  red  Bundner  wine.10  Etti  obtained  it  by  heating 

1  Chem.  Centralbl.  1858,  579.  2  Pkarm.  Centralbl.  1855,  658. 

3  Chem.  Soc.  Mem.  i.  p.  147.  4  Ann.  Chem.  Pharm.  cxliii.  295. 

5  Journ.  PraJct.  Chem.  cii.  Ill  j  ciii.  446. 

6  Freseniits'  Zeitschr.  xi.  365. 

7  Stenhouse,  Chem.  Soc.  Mem.  i.  137. 

8  Kawalier,  Jahresb.  Chem.  1852,  683. 

9  Hlasiwetz  and  Malin,  Zeitschr.  Chem.  1867,  271. 
10  Simler,  Jahresb.  Chem.  1861.  923. 


GALLIC  ACID.  367 


kinoin,  C14H12O6,  with  hydrochloric  acid ; l  it  is  also  formed 
when  di-iodoparahydroxybenzoic  acid,2  bromoprotocatechuic  acid,3 
bromoveratric  acid,4  and  a-bromoresorcylic  acid,5  are  fused  with 
caustic  potash.  According  to  Lautemann  it  is  also  formed  in 
this  way  from  di-iodosalicylic  acid,6  but  Demole  failed  to  obtain 
it  by  this  method,7  and  it  is  probable  that  Lautemann's  com- 
pound, which  was  only  obtained  in  small  quantity,  is  the  isomeric 
pyrogallolcarboxylic  acid. 

In  order  <to  prepare  gallic  acid,  Scheele's  method,  which  is 
stated  by  Liebig  to  give  the  best  yield,  is  made  use  of.  Finely 
powdered  nut-galls  are  extracted  with  cold  water  and  the  solution 
allowed  to  stand  in  a  warm  place,  the  precipitated  acid  being 
recrystallized  from  boiling  water. 

According  to  Braconnot,  the  entire  nut-galls  may  be  moistened 
with  water  in  summer  or  allowed  to  stand  in  a  warm  place  until 
they  form  a  paste,  which  is  then  extracted  with  boiling  water.8 

The  spores  of  Penicillium  glaucum  or  Aspergillus  niger  are 
necessary  to  set  up  fermentation.9  Wittstein  recommends  the 
addition  of  beer  yeast ;  he  thus  obtained  almost  50  per  cent, 
from  Chinese  nut-galls,  while  without  the  yeast  the  yield  only 
amounted  to  17  per  cent.10  One  hundred  pounds  of  Turkish 
nut-galls,  treated  by  Scheele's  method,  give  24  pounds  of  gallic 
acid.11 

It  crystallizes  in  silky  needles  or  asymmetric  prisms,  containing 
one  molecule  of  water,  which  is  lost  at  120°,  has  an  acid, 
astringent  taste,  and  dissolves  in  130  parts  of  water  at  12'5°,  and 
in  3  parts  at  100°.  It  is  more  readily  soluble  in  alcohol,  since 
27'95  parts  dissolve  in  100  parts  of  absolute  alcohol  at  15°, 
and  18*90  parts  in  100  parts  of  90  per  cent,  alcohol,  while  100 
parts  of  ether  only  dissolve  2 '5  parts.12 

Gallic  acid  commences  to  melt  above  220°  and  decomposes 
into  carbon  dioxide  and  pyrogallol  when  more  strongly  heated. 
It  is  readily  oxidized,  reduces  Fehling's  solution  and  the  salts  of 
the  noble  metals,  and  in  alkaline  solution  absorbs  oxygen.  When 

1  Ber.  Deutsch,  Chem.  Ges.  xi.  1881. 

2  Earth  and  Senhofer,  ibid.  viii.  1884. 

3  Ibid.  4  Matmoso,  ibid.  xi.  140. 
6  Barth  and  Senhofer,  Ann.  Chem.  Pharm.  clxiv.  118. 

6  Ibid.  cxx.  137. 

7  Ber.  Dcutfteh.  Chem.  Gcs.  vii.  1441. 

8  Ann.  Chim.  Phys.  ix.  181. 

9  Tieghem,  Zeitschr.  Chem.  1868,  222. 

10  Vierteljahrsschr.  Pharm.  ii.  72. 

11  Steer,  Jahresber.  Chem.  1856,  482. 

12  Bourgoin,  Bull.  Soc.  Chim.  xxix.  245. 


368  AROMATIC  COMPOUNDS. 

it  is  added  to  feme  chloride,  a  partial  reduction  ensues 
and  a  black-blue  precipitate  is  formed,  which  dissolves  in  the 
excess  of  ferric  chloride  with  a  green  colour.  According  to 
Etti,  the  colouration  depends  mainly  on  the  concentration  of 
the  solutions,  and  varies  between  black-blue,  black -green,  blue, 
greenish  and  brownish  green.  An  excess  of  gallic  acid  destroys 
the  colour  and  effects  complete  reduction  to  ferrous  chloride  ;  a 
solution  of  pure  ferrous  sulphate  in  absence  of  air  is  therefore 
not  altered  by  it,  but  on  exposure  to  air  is  coloured  a  bright  blue, 
and  deposits  a  black  precipitate  without  becoming  decolourized. 

Gallic  acid  in  alcoholic  or  alkaline  solution  reduces  paranitro- 
benzyl  chloride  to  paranitrotoluene.  Digallic  acid  and  pyro- 
gallol  have  a  similar  action.1 

It  is  converted  by  the  action  of  potassium  chlorate  and 
hydrochloric  acid  into  tricarballylic  acid,  C3H5(CO2H)3,  and 
isotrichloroglyceric  acid,  CC13.C(OH)2.C02H,  which  crystallizes  in 
needles  and  is  readily  decomposed  by  alkalis  into  chloroform  and 
oxalic  acid.2 

When  gallic  acid  is  heated  with  sulphuric  acid,  rufigallic  acid 
or  hexyhydroxyanthraquinone,  CUH2O2(OH)6,  is  formed,  while  an 
acid  solution  of  potassium  permanganate  produces  hydrorufigallic 
acid,  C14H8O5. 

Gallic  acid  is  not  precipitated  by  gelatine  solution,  and  can 
thus  be  distinguished  from  tannic  acid  and  other  similar 
substances. 

2203  The  G-allates  have  been  chiefly  investigated  by  Buchner. 

Sodium  gallate,  C6H2(OH)3C02Na  +  3H2O,  is  obtained  by 
adding  alcoholic  soda  to  a  solution  of  the  acid  in  alcohol  as  a 
granular,  crystalline  precipitate,  which  crystallizes  from  a  very 
concentrated  aqueous  solution  in  pointed  yellow  plates. 

Potassium  gallate,  C6H2(OH)3CO2K  +  C6H2(OH)3C02H+H20, 
is  a  light,  crystalline  powder  which  is  prepared  in  a  similar 
manner  to  the  sodium  salt ;  the  normal  salt  has  not  yet  been 
obtained. 

Ammonium  gallate,  C6H2(OH)3CO2NH4  +  H2O,  is  formed 
when  ammonia  is  passed  into  a  solution  of  the  acid  in  absolute 
alcohol,  and  crystallizes  from  water  in  fine  needles.  When  its 
solution  is  boiled,  the  acid  salt,  C6H2(OH)3C02NH4  +  C6H2(OH)3 
C02H,  is  deposited  on  cooling  in  splendid  crystals.3  It  is  also 

1  Pellizzari,  Gazz  Chem.  Itnl.  xiv.  481. 

2  Schreder,  Ann.  Chem.  Pharm.  clxxvii.  282  ;  see  also  Claisen  and  Antweiler, 
Ber.  Deutsch.  Chem.  Ges.  xiii.  1938. 

3  Etti,  Ber.  Deutsch.  Chem.  Ges.  xvii.  1821. 


SALTS  OF  GALLIC  ACID. 


formed  when  dry  gallic  acid  is  saturated  with  ammonia,  the 
excess  of  the  latter  allowed  to  evaporate  in  a  vacuum  and  the 
residue  crystallized  from  water ;  it  contains  water  of  crystallization 
(Kobiquet). 

Calcium  gallate,  (C7H505)2Ca  4-  3H20,  forms  thin,  crystalline 
crusts,  consisting  of  needles.  When  lime-water  is  added  to  a 
solution  of  the  acid  a  dirty  green  precipitate  is  produced. 

Barium  gallate,  (C7H5O5)2Ba  +  3H2O,  is  obtained  by  neutra- 
lizing a  boiling  solution  of  the  acid  with  barium  carbonate ;  it 
crystallizes  in  small  plates,  which  do  not  readily  redissolve  in 
water.  If  the  freshly-prepared  solution  be  treated  with  baryta- 
water,  a  precipitate  of  C7H205Ba2  +  5H2O  is  formed,  which 
rapidly  becomes  coloured  dark  blue  on  exposure  to  the  air  in  the 
moist  state  (Hlasiwetz). 

Lead  gallate.  Lead  acetate  added  to  a  hot  solution  of  an 
excess  of  the  acid  produces  a  precipitate  of  2C7H4O5Pb  -f  H2O, 
which  soon  changes  to  a  lustrous,  crystalline  powder.  If,  how- 
ever, an  excess  of  the  lead  acetate  be  employed,  a  flocculent 
precipitate  is  formed,  which  becomes  yellow  and  crystalline  on 
boiling  and  has  the  formula  C7H205Pb2  (Liebig). 

Iron  gallate.  A  splendid  blue  precipitate  is  obtained  when 
the  acid  is  added  to  a  mixture  of  three  molecules  of  a  ferrous 
salt  with  two  molecules  of  a  ferric  salt.1 

Ethyl  gallate,  2C6H2(OH)3C02.C2H5  +  5H2O,  is  formed  when 
hydrochloric  acid  is  passed  into  the  alcoholic  solution  of  the  acid. 
It  is  slightly  soluble  in  cold,  readily  in  hot  water  and  alcohol, 
and  crystallizes  in  pointed  prisms,  which  lose  their  water  at 
1000.2  It  is  slightly  soluble  in  chloroform,  from  which  it 
separates  in  anhydrous  crystals.3  It  behaves  towards  ferric 
chloride,  silver  nitrate,  &c.,  in  the  same  manner  as  the  free 
acid,  and  on  heating  decomposes  into  alcohol  and  pyrogallol, 
accompanied,  however,  by  other  products.4  When  acid  sodium 
carbonate  is  added  to  its  aqueous  solution,  small  crystals  of 
C6H2(OH)3C02.C2H5  +  C6H2(OH)2(ONa)C02.C2H5,  are  formed, 
which  are  scarcely  soluble  in  cold  water  (Ernst  and  Zwenger). 
Lead  acetate  added  to  an  aqueous  solution  of  the  ether  produces 
a  finely  divided  precipitate  of  (C6H2(CO2.C2H5)03)2Pb3  (Schiff). 

Triethylgallic  acid,  C6H2(OC2H5)3CO2H.  The  ethyl  ether  of 
this  substance  is  obtained  by  heating  ethyl  gallate  with  caustic 

1  Barreswill,  Compt.  Rend.  xvii.  739. 

2  Grimaux,  Bull.  Soc.  Chim.  ii.  94. 

3  Ernst  and  Zwenger,  Ann.  Chem.  Fharm.  clix.  28. 

4  Schiff,  ibid,  clxiii.  209. 


370  AROMATIC  COMPOUNDS. 

potash,  ethyl  iodide  and  alcohol ;  water  precipitates  it  from  alco- 
holic solution  in  lustrous  needles,  which  melt  at  51°  and  are  easily 
decomposed  by  alcoholic  potash ;  hydrochloric  acid  separates  the 
triethylgallic  acid  from  the  product  as  a  crystalline  precipitate. 
It  is  slightly  soluble  in  cold,  readily  in  hot  water,  and  separates 
from  the  latter  in  crystals  melting  at  1120.1 

Triacetylgcillic  acid,  C6H2(OC2H3O)3CO2H,  is  prepared  by 
boiling  gallic  acid  with  acetyl  chloride  and  acetic  anhydride.  It 
is  only  slightly  soluble  in  hot  water,  separates  from  alcohol  in 
small,  lustrous  needles  and  gives  no  colouration  with  ferric 
chloride  (Schiff). 

Bromogallic  acid,  C6HBr(OH)3CO2H,  is  obtained  by  triturating 
equal  molecules  of  gallic  acid  and  bromine.2  It  separates  from 
the  hot,  aqueous  solution  in  monoclinic  crystals,  resembling  those  of 
gypsum  ;  its  solution  gives  a  splendid  violet  colouration  with  ferric 
chloride  and  a  fiery  red,  soon  changing  to  brown  with  ammonia. 

Dibromogallic  acid,  C6Br2(OH)3CO2H  4-  H20,  is  formed  when 
an  excess  of  bromine  is  employed  (Grimaux).  It  crystallizes 
from  hot  water  in  long  plates  or  needles,  melting  at  1500.3  Ferric 
chloride  produces  a  black-blue  colouration ;  moist  silver  oxide 
decomposes  it  with  formation  of  pyrogallol,  carbon  dioxide  and 
silver  bromide,  while  on  heating  with  water  and  potassium  silver 
cyanide  it  is  reconverted  into  gallic  acid  : 4 

C6Br2(OH),C02H  +  2AgCN  +  4H2O  = 
C6H2(OH3)C02H  +  2C02  +  2NH3  +  2AgBr. 

Gallamide,  C6H2(OH)3CO.NH2.  This  compound,  which  is  also 
called  gallamic  acid,  is  formed  together  with  gallic  acid  when  a 
solution  of  tannin  in  ammonia  is  rapidly  boiled : 

H(X  OH 

H(X  /OH 


x  +  NH    =        XC  H  / 
HO^  /O  HO/         \CO.NHj 

\CO.OH 

HO.  /OH 


CO.OH. 

.  Ges.  xvii. 
9  ;  Grimaux 
8  Etti,  Bcr.  Deuisch.  Chem.  Ges.  xi.  1182.  4  Priwoznik,  ibid.  iii.  645. 


1  Albrecht  and  Will,  Bcr.  Dcutsch.  Chem.  Ges.  xvii.  2098. 

2  Hlasiwetz,  Ann.  Chem.  Pharm.  cxlii.  249  ;  Grimaux,  Zeitschr.  Chem.  1867,  431. 


TANNIC  ACID.  371 


In  order  to  avoid  oxidation,  ammonium  sulphite  must  be 
added  to  the  solution  or  the  operation  must  be  conducted  in 
an  atmosphere  free  from  oxygen.1  It  crystallizes  from  hot  water 
in  large,  colourless  plates  and  decomposes  on  boiling  with 
hydrochloric  acid  into  gallic  acid  and  ammonia. 

2204  Digallic  acid,  Tannic  acid  or  Tannin,  C6H2(OH)3CO. 
OC6H2(OH)2C02H.  The  name  of  tannic  acids  has  been  applied 
to  a  whole  series  of  substances,  which  are  weak  acids,  "have  an 
astringent  taste,  give  black-blue  or  dark  green  compounds  with 
salts  of  iron,  and  combine  with  animal  skins  to  form  leather,  for 
which  purpose  they  are  largely  employed.  These  bodies  do  not 
stand  in  any  intimate  chemical  relation  to  each  other,  and  the 
tannic  acid  derived  from  nut-galls,  the  constitution  of  which  is 
known,  is  alone  referred  to  here. 

The  nut-galls  in  which  it  occurs  are  of  two  kinds  :  the  ordinary, 
Turkish  or  Levant  variety,  which  are  produced  by  the  puncture 
of  the  gall-fly  (Cynips  G-allae  tinctoriae)  in  the  young  shoots  of 
Quercus  hisitanica,  var.  infectoria  and  probably  some  other 
species,  and  the  Chinese  or  Japanese  nut-galls,  which  are  formed 
by  a  plant-louse  (Aphis  chinensis)  on  the  leaf-stalks  and  young 
twigs  of  Rhus  semialata.  In  addition  to  these  modes  of  occur- 
rence, tannic  acid  has  hitherto  only  been  observed  in  sumach, 
the  leaves  and  twigs  of  Rhus  coriaria.2 

Stenhouse,  who  found  that  tannic  acid  from  sumach  is  con- 
verted into  gallic  acid  by  dilute  sulphuric  acid,  says :  "  Sumach, 
therefore,  appears  to  approach  the  nature  of  nut-galls  more 
closely  than  any  of  the  other  astringent  substances.  This  fact 
is  well  known  to  Turkey-red  dyers,  who  have  long  successfully 
employed  sumach  as  a  substitute  for  galls." 

In  order  to  prepare  tannin,  the  method  of  Pelouze  was  formerly 
employed,  according  to  which  the  nut-galls  are  extracted  with 
ordinary  ether,  containing  both  alcohol  and  water.  The 
solution  thus  obtained  separates  into  two  layers,  the  upper  of 
which  consists  of  water  and  ether  containing  gallic  acid  and  a 
little  tannin,  while  the  syrupy  lower  layer  is  a  solution  of  tannin 
in  water  and  ether  and  is  evaporated  to  dryness. 

A  mixture  of  12  parts  of  ether  and  3  parts  of  alcohol  is  now 
used  for  the  extraction,  12  parts  of  water  being  added  to  the 
extract  and  the  alcohol  and  ether  removed  by  distillation.  The 

1  Knop,  Jahrcsber.   Chem.  1854,  431  ;  Schiff  and  Pons,  Per.  Deutsch.  Chem. 
Ges.  xv.  2591  ;  xviii.  487  ;  Etti,  ibid.  xvii.  1820. 

2  Stenhouse,  C/WM.  Soc.  Mem.  i.  137  ;  Lowe,  Fres.  Zeitschr.  xii.  128. 


372  AROMATIC  COMPOUNDS. 

residual  aqueous  solution  is  then  filtered  and  evaporated,  the 
crude  tannin  being  further  purified  by  solution  in  water  and 
treatment  with  animal  charcoal.1 

Pure  tannin  may  also  be  obtained  by  extracting  nut-galls 
with  anhydrous  ether,  to  which  5  per  cent,  of  alcohol  has  been 
added  (Schiff). 

While  the  tannin  prepared  by  Pelouze's  method  contains  more 
or  less  grape  sugar  or  a  substance  yielding  dextrose,  this  is  not 
the  case  with  that  obtained  by  the  more  modern  process,  and 
hence  it  follows  that  tannin  is  not  a  glucoside,  but  that  the  older 
specimens  contained,  as  was  suggested  by  Rochleder,  an  admix- 
ture of  sugar  or  a  glucoside  which  was  brought  into  solution  by 
the  water  present.2 

Schiff,  as  already  mentioned,  found  that  gallic  acid  is  converted 
into  tannic  acid  when  it  is  heated  with  phosphorus  oxychloride 
or  when  its  solution  is  evaporated  with  arsenic  acid.  According 
to  Freda,  the  product  obtained  by  the  latter  method  gives  all 
the  characteristic  reactions  of  tannin,  but  is  nothing  more  than 
gallic  acid  containing  arsenic  acid,3  while  Schiff  has  shown  that 
this  is  not  the  case,  but  that  arsenic  acid  adheres  to  the  tannin 
so  obstinately  that  it  cannot  be  removed  without  a  simultaneous 
conversion  of  a  portion  of  the  latter  into  gallic  acid.4  The 
constitution  of  tannin  or  digallic  acid  is  expressed  by  the 
following  formula : 

HOv  ,HO 

"2\co> 
/° 

HO/         \CO.OH. 

This  explains  in  a  simple  manner  its  conversion  into  gallic  acid 
by  the  assumption  of  water,  its  decomposition  into  gallamide  and 
gallic  acid  by  the  action  of  ammonia  and  the  formation  of 
a  penta-acetyl-derivative. 

The  fact  that  when  monobromocatechuic  acid  is  heated 
with  potassium  gallate  and  alcohol,  a  substance  is  formed 

1  Biedermann,  Bcr.  Entw.  Chem.  Ind.  ;  2  Halfte,  p.  456. 

2  Schiff,  Ann.  Chem.  Plwrm.  clxx.  75. 
8  Ber.  Deutsch.  Chem.  Ges.  xii.  1576. 

4  Ibid.  xiii.  454. 


PROPERTIES  OF  TANNIN.  373 

which  gives  all  the  reactions  of  tannin,  is  also  in  favour  of  this 
formula : 1 

C6H9(OH)3CO.OK  +  BrC6H2(OH)2CO.OH  = 
CX(OH)3CO.O.C6H2(OH)2CO.OH  +  KBr. 

Properties. — Tannin  is  a  colourless,  amorphous  mass,  which  is 
left  on  the  evaporation  of  its  solution  in  brittle,  vitreous  masses, 
which  become  coloured  yellow  in  the  light,  even  when  exposed 
in  closed  vessels.  It  reddens  litmus  and  has  a  very  strong 
astringent  taste,  is  readily  soluble  in  water,  less  so  in  absolute 
alcohol,  and  almost  insoluble  in  absolute  ether.  Finely-powdered 
tannin  coagulates  in  ether  which  contains  water,  and  then  de- 
liquesces, so  that  it  can  be  employed  to  detect  the  presence  of 
water  in  ether.  If  water  be  slowly  dropped  into  the  vessel 
containing  the  thick  solution  covered  by  ether,  a  point  is 
attained  at  which  three  layers  are  formed.2  This  occurs  when 
100  ccms.  of  water  and  150  ccms.  of  ether  are  present  to  100 
grms.  of  tannin  ;  the  lowest  layer  contains  most  tannic  acid,  the 
middle  layer  some  tannic  acid  and  a  large  amount  of  water 
while  the  upper  layer  consists  almost  entirely  of  ether,  but 
contains  a  little  tannic  acid.3 

Tannin  is  insoluble  in  carbon  disulphide,  chloroform,  petroleum 
ether,  benzene,  &c.  Its  aqueous  solution  gives  a  black-blue 
colouration  and  precipitate  with  ferric  salts,  a  partial  reduction 
taking  place  (Wackenroder) ;  ferrous  sulphate  produces  in  a 
concentrated  solution  a  white,  gelatinous  precipitate  which 
becomes  coloured  blue  in  the  air. 

When  tannin  is  heated  it  darkens  at  150°— 160°,  and  at  215° 
decomposes  into  water,  carbon  dioxide  and  pyrogallol,  which 
volatilize,  while  metagallic  acid  or  melangallic  acid  is  left 
behind;  this  substance  alone  is  formed  when  tannic  acid  is 
rapidly  heated  to  250°,  and  is  a  black,  amorphous,  tasteless 
mass.  Tannin  very  readily  undergoes  oxidation;  strongly 
ozonized  air  produces  complete  combustion,  oxalic  acid  being 
formed  as  an  intermediate  product  (Schonbein) ;  it  reduces  the 
salts  of  copper,  silver,  mercury,  gold,  &c.  In  alkaline  solution 
it  rapidly  absorbs  oxygen,  the  liquid  becoming  coloured  dark. 
Tannin  is  precipitated  from  aqueous  solution  by  dilute  hydro- 
chloric acid,  sulphuric  acid,  common  salt,  potassium  chloride, 

1  Hunt,  Chem.  News,  lii.  49. 

2  Bolley,  Ann.  Chem.  Pharm.  cxv.  63. 

3  Luboldt,  Jahresb.  Chem.  1859,  296. 

255 


374  AROMATIC  COMPOUNDS. 

potassium  acetate  and  other  salts,  but  not  by  nitric   acid   or 
sodium  sulphate.     Animal  skin  removes  it  from  solution  com-  - 
pletely ;  it  precipitates  gelatine  solution,  egg  albumen,  alkaloids 
and  other  substances. 

The  Tannates.  Tannin  decomposes  carbonates  and  is  a  mono- 
basic acid,  the  salts  of  which  are  amorphous  and  difficult  to 
prepare  pure.  Many  of  them  are  insoluble  precipitates,  such  as 
the  tannates  of  lead,  copper,  tin,  and  antimony,  and  these  may 
be  used  for  the  quantitative  estimation  of  the  acid. 

Tannin,  or  rather  the  material  containing  it,  is  employed  in 
medicine,  dyeing,  the  manufacture  of  inks,  the  clarification  of 
beer  and  wine,  &c.  It  is  not  adapted  for  use  as  a  tanning 
agent. 

Penta-acetyltannin,  C14H5(C2H3O)5O9,  is  obtained  by  boiling- 
tannin  with  acetic  anhydride  for  one  hour ;  it  is  insoluble  in 
water  and  separates  from  boiling  alcohol  in  white  spherical  or 
warty  aggregates  of  crystals,  which  melt  at  137°.  Its  solution 
is  precipitated  by  lead  acetate,  but  is  not  coloured  by  ferric 
chloride  (Schiff). 

Kino'in,  CUH12O6,  was  discovered  by  Etti  in  Malabar  kino,  the 
dried  sap  of  Pterocarpus  Marsupium  (p.  351).  It  crystallizes  in 
prisms,  which  are  slightly  soluble  in  cold,  readily  in  hot  water 
and  alcohol ;  its  solution  is  coloured  red  by  ferric  chloride.  On 
heating  to  120°  with  hydrochloric  acid,  it  decomposes  into  methyl 
chloride,  catechol  and  gallic  acid  : 

C14H1206  +  H20  +  HC1  =  CH3C1  +  C6H6O2  4-  C7H6O5. 

It  is  therefore  gallylcatechol  methyl  ether,  and  probably  has 
the  following  constitution : 

HOV  /OH 

>C6H2< 
EKK          \CO.OC6H4.OCH3. 

Kino-red,  C28H22On,  is  an  astringent  substance  which  also 
occurs  in  kino,  and  is  formed  by  heating  kinoin  to  120° — 130°. 
It  is  a  red,  resinous  substance,  which  is  slightly  soluble  in  water, 
readily  in  alcohol  and  alkalis,  gives  a  dirty-green  colouration 
with  ferric  chloride,  and  precipitates  gelatine  solution.  On 
heating  to  160° — 170°,  it  melts  with  loss  of  water  and  is 
converted  into  an  amorphous  red  compound,  C28rI20Ol0,  which 
may  also  be  obtained  by  heating  kino-red  with  dilute  hydro- 
chloric or  sulphuric  acids.  On  dry  distillation,  the  larger 


SLNAPIN.  375 


portion    becomes    carbonized,    phenol,    catechol    and    a    small 
amount  of  anisol  or  guaiacol  being  formed.1 

2205  Sinapin,  CIQH.J$O5.  Henry  and  Garot  discovered  in 
the  seeds  of  the  white  mustard,  a  crystalline  compound,  con- 
taining both  sulphur  and  nitrogen,  to  which  they  gave  the 
name  of  sulphosinapin,2  and  which  was  subsequently  recognized 
by  Babo  and  Hirschbrunn  as  sinapin  thiocyanate.3  Robiquet 
and  Boutron  Charlard,  repeating  the  research  of  Henry  and 
Garot,  obtained  another  substance,4  which  Will  and  Lauben- 
heimer  named  sinalbin,  and  which  is  resolved  into  acid  sinapin 
sulphate,  sinalbin  mustard  oil,  and  grape  sugar,  by  the  action  of 
myrosin  in  aqueous  solution  (Vol.  III.,  Part  II.,  p.  393). 

Sinapin,  which  is  generally  classed  among  the  alkaloids,  is 
extremely  deliquescent,  but  forms  stable  salts. 

Sinapin  thiocyanate,  C16H23N05.HSCN,  is  obtained  from  the 
powdered  seeds  by  first  extracting  them  with  ether  and  cold 
alcohol,  and  then  boiling  up  with  90  per  cent,  alcohol.  A  very 
voluminous  crystalline  mass,  which  bears  a  strong  resemblance 
to  quinine  sulphate,  separates  out  on  cooling.  It  crystallizes 
from  a  dilute,  hot,  aqueous  solution  in  large,  fascicular  groups  of 
needles,  which  melt  at  1760,5  and  are  only  slightly  soluble  in  cold 
alcohol  and  water. 

Acid  sinapin  sulphate,  C16H23N05,H2SO4  +  2H2O,  is  obtained 
by  adding  sulphuric  acid  to  a  concentrated,  hot  solution  of  the 
thiocyanate  ;  it  crystallizes  in  rectangular  plates,  has  an  acid 
reaction  and  is  readily  soluble  in  water. 

The  normal  sulphate  may  be  prepared  from  the  acid  by 
neutralizing  with  baryta  water  and  evaporating  the  filtrate; 
it  forms  an  extremely  soluble  crystalline  mass.  The  nitrate 
and  hydrochloride  of  sinapin  can  be  prepared  from  it  by  means 
of  barium  nitrate  or  chloride,  and  crystallizes  in  fine,  very 
soluble  needles.  The  hydrochloride  combines  with  mercuric 
chloride  to  form  the  compound  C16H23NO5,HC1  +  HgCl2,  which 
crystallizes  from  water  in  thin,  lustrous  prisms  (Will  and 
Laubenheimer). 

When  the  sulphuric  acid  is  completely  removed  by  baryta 
water  from  a  solution  of  the  sulphate,  a  solution  of  free  sinapin 
is  obtained  which  has  a  deep  yellow  colour,  is  alkaline  to  litmus, 

1  Ber.  Deutsch.  Chem.  Ges.  xi.  1879. 

2  Berzelius,  Jahresber.  vi.  242  ;  xii.  263. 

3  Ann.  Chem.  Pharm.  Ixxxiv.  10. 

4  Ibid.  xii.  266. 

6  Remsen  and  Coale,  Amer.  Chem.  Journ.  vi.  50. 


376  AROMATIC  COMPOUNDS. 

and  precipitates  the  salts  of  the  heavy  metals.  It  decomposes 
on  evaporation,  the  colour  changing  through  green  and  red  into 
brown  and  a  noncrystalline  residue  being  left. 

If  sinapin  thiocyanate  be  boiled  with  baryta  water  or  caustic 
potash  solution,  it  decomposes  into  thiocyanic  acid,  sinapic  acid 
and  a  base,  which  was  named  sinkalin  by  Babo  and  Hirsch- 
brunn,  but  has  since  been  identified  as  choline  (Vol.  III.,  Part 
II,  p.  64). 

C^H^NO^HSCN  +  2H20  =  HSCN  +  CUHI2O6  +  C16H15NO2. 

Sinapic  acid,  CnH12O5,  is  best  prepared,  according  to  Remsen 
and  Coale,  by  boiling  sinapin  with  baryta  water  and  decom- 
posing the  precipitate,  which  is  formed,  with  hydrochloric  acid. 
It  is  only  slightly  soluble  in  cold  water  and  alcohol,  and  crystal- 
lizes from  a  hot  solution  in  small,  yellowish,  transparent  prisms, 
melting  at  192°.  Its  alkaline  solution  rapidly  turns  green,  red, 
and  brown  in  the  air.  The  addition  of  alcohol  to  the  freshly 
prepared  solution  of  the  potassium  salt  precipitates  it  in 
iridescent  plates,  which  rapidly  change  after  the  removal  of  the 
alcohol.  Calcium  chloride  and  barium  chloride  produce  white 
precipitates,  and  ferric  chloride  gives  a  rose-red  or  fine  purple- 
red  precipitate,  a  partial  reduction  being  also  effected.  Lead 
salts  added  to  a  neutral  solution  of  the  acid  produce  a  white 
precipitate,  which  soon  becomes  green  and  then  brown,  while 
the  colourless  precipitates  yielded  by  the  salts  of  silver  and 
mercury,  are  rapidly  reduced ;  the  metal  is  immediately 
separated  from  gold  solutions. 

The  barium  salt  alone  has  been  obtained  in  a  condition 
suitable  for  analysis  by  precipitating  a  solution  of  the  acid, 
neutralized  by  potash  or  ammonia,  with  barium  chloride,  or 
more  readily  by  boiling  the  acid  with  baryta  water  in  absence 
of  air  ;  it  has  the  composition  CnH10Ba05. 

Babo  says :  "  Since  it  is  a  matter  of  some  difficulty  to  obtain 
another  salt  of  the  acid  in  a  state  fitted  for  analysis,  and  I  could 
not  spare  too  much  material  for  this  research,  the  question 
whether  the  acid  is  mono-  or  dibasic  must  remain  for  the 
present  undecided." 

This  point  was  settled  by  Remsen  and  Coale,  who  heated 
weighed  amounts  of  the  acid  with  calcium  or  barium  carbonate 
and  determined  the  amount  of  metal  which  had  entered  into 
solution ;  they  found  that  sinapic  acid  is  monobasic,  and  that 
the  normal  barium  salt  has  the  formula  (CnHnO5)2Ba. 


SINAPIC  ACID.  377 


The  insoluble  barium  salt  is  therefore  a  basic  compound, 
corresponding  to  the  basic  salicylates,  and  sinapic  acid  should 
therefore  be  a  hydroxy-acid,  as  is  proved  to  be  the  case  by  the 
existence  of  the  following  compound. 

Acetylsinapic  acid,  C11H11(C2H30)05,  is  obtained  by  boiling 
the  acid  with  acetic  anhydride,  and  forms  crystals,  which  are 
soluble  in  hot  water  and  melt  at  281°. 

When  sinapic  acid  is  heated  on  platinum  foil,  vapours  are 
given  off  which  smell  like  incense,  and  are  also  formed  when 
the  acid  is  fused  with  caustic  potash,  pyrogallol  being  among 
the  products. 

According  to  Remsen  and  Coale,  sinapic  acid  is  probably 
butylenegallic  acid  : 


C6H2 

\CO.OH. 


If  this  view  be  correct,  the  following  formulae  will  represent 
the  constitution  of  sinapin  and  its  thiocyanate  : 


6 

XX  \CO.OC2H4N(CH3)3OH. 

X°\  XOH 

C4H8<     >C6H  / 

XX  \CO.OC2H4N(CH3)3S.CN. 

If  it  be  further  assumed  that  sinalbin  contains  two  molecules 
of  water  of  crystallization,  its  constitution  may  be  represented 
as  follows  : 

XX  XOC6HU06 

C  H  '      ^C  H  ' 

N)/         \CO.O.C2H4(CH3)3NO.S02.OC6H4.CH2.NCS. 

Grallocyanin.  This  dye,  which  was  discovered  by  Kochlin, 
and  which  is  also  known  as  solid-violet  (violet  solide),  is  manu- 
factured by  heating  nitrosodimethylaniline  hydrochloride  with 
gallic  acid  or  tannin  in  alcoholic  solution.  It  is  a  crystalline 
substance  with  a  green  metallic  lustre,  readily  dissolves  in 
alkalis,  and  yields  salts  which  crystallize  well,  that  with  aniline 
forming  small,  green  crystals.  Gallocyanin  forms  a  blue  solution 
in  concentrated  sulphuric  acid.  It  is  used  for  dyeing  cotton 
and  in  calico  printing,  since  it  forms  a  beautiful  violet-  black 


378  AROMATIC  COMPOUNDS. 

lake  with  chromium  oxide,  with  which  the  material  is  mordanted. 
The  shades  produced  are  as  bright  as  those  of  aniline  violet,  but 
much  more  stable  towards  light,  alkalis  and  acids.  In  the 
presence  of  quercitron  or  similar  yellow  dyes,  dark  blue  shades 
resembling  indigo  are  produced  and  can  be  varied  to  the 
greenest  shades  of  blue. 

It  dyes  silk  and  wool  directly  violet-blue,  and  is  also  used  as  an 
acid  blue  on  azo-colours ;  the  goods  are  dyed  in  ponceau  or  some 
other  shade,  and  the  pattern  is  then  printed  on  in  the  shape  of 
a  mixture  of  solid-violet,  indophenol  and  an  alkaline  reducing 
agent,  which  effects  the  usual  decomposition  of  the  azo-coiour, 
while  the  blue  colours  are  reduced  to  leuco-compounds,  which 
penetrate  the  fibre  and  on  exposure  to  air  produce  a  fast  blue 
on  a  red  ground.1 

Gallocyanin  belongs  to  the  class  of  the  indophenols,  but  its 
analysis  has  not  yet  been  published.  Its  method  of  formation 
leads  to  the  following  constitution  or  some  similar  one  (Part  III., 
p.  331). 

Hx  XC02H 

\Q Q/ 

0—C(         '\C=N.C6H4.N(CH3)2. 

>C=C< 
OH/  X)H 


PYROGALLOLCARBOXYLIC  ACID. 

2206  This  compound  is  formed,  together  with  gallocarboxylic 
acid,  C6H(OH)3(C02H)2,2  by  heating  pyrogallol  to  130°  with 
ammonium  carbonate,  or  more  simply  by  heating  pyrogallol  in 
an  open  flask  with  a  concentrated  solution  of  acid  potassium 
carbonate.8  It  crystallizes  from  hot  water  in  silky  needles  of  the 
composition  3C6H2(OH)3CO2H  -f  H2O,  which  become  anhydrous 
at  110°  and  have  a  markedly  acid  taste.  One  part  dissolves  at 
12'5°  in  767  parts  of  water ;  it  is  readily  soluble  in  alcohol,  but 
less  so  in  ether.  On  heating  in  a  current  of  hydrogen,  a  gradual 
evolution  of  carbon  dioxide  accompanied  by  fusion  sets  in  at 
195° — 200°,  while  it  sublimes  slowly,  but  without  decomposition, 
in  a  current  of  carbon  dioxide.  Its  aqueous  solution  is  coloured 

1  Kochlin,  Chem.   News,  xlvii.   170 ;  Pabst,  Bull.  Soc.  Chim.  xxxviii.  162  ; 
ChemiTcerzeit,  ix.  1444. 

2  Senhofer  and  Branner,  Monatsh.  Chcm. .  i.  468. 

3  Kostanecki,  Ber.  Deutsch.  Chem.  Ges.  xviii.  3202. 


PYROGALLOL  CARBOXYLIC  ACID.  379 

violet  by  very  dilute  ferric  chloride,  while  a  strong  solution  pro- 
duces a  greenish  brown  colouration ;  ferrous  sulphate  produces  no 
immediate  colouration,  but  the  liquid  becomes  violet  on  stand- 
ing. The  same  colouration  is  produced  by  concentrated  sulphuric 
acid  which  contains  a  trace  of  nitric  acid. 

Baryta  water  and  lime  water  produce  blue  precipitates  which 
are  at  first  so  finely  divided  that  the  liquid  appears  clear.  The 
acid  is  coloured  dark  brown  by  strong  potash  solution,  especially 
on  boiling.  It  reduces  ammoniacal  silver  solution  in  the  cold 
and  imparts  a  green  colour  to  Fehling's  solution,  reduction  taking 
place  on  warming. 

It  differs  sharply  from  gallic  acid  in  remaining  unacted  on 
by  sulphuric  acid  at  140°,  no  rufigallic  acid  being  formed ;  de- 
composition, accompanied  by  a  violent  evolution  of  gas,  sets  in, 
however,  at  a  higher  temperature. 

The  Pyrogallokarboxylates.  The  following  salts  are  charac- 
teristic : 

Calcium  pyrogallolcarboxylate,  (G7H5O5)2Ca  +  4H20,  separates 
from  a  hot  solution  in  hard,  granular  crystalline  masses. 

Barium  pyrogallolcarboxylate,  (C7H5O5)2Ba  +  5H2O,  crystallizes 
from  a  hot  solution  in  hard,  yellow  prisms. 

Basic  lead  pyrogallolcarboxylate,  C7H2Pb2O5  +  H2O,  is  a  white, 
flocculent  precipitate,  which  becomes  anhydrous  at  100°. 

Ethyl  pyrogallolcarboxylate,  2C6H2(OH)3CO2.C2H5  +  3H2O,  is 
insoluble  in  cold  water,  but  readily  in  alcohol  and  ether,  and 
separates  from  a  hot  aqueous  solution  in  crystals,  which  become 
anhydrous  over  sulphuric  acid  or  at  100°,  at  which  temperature 
they  commence  to  sublime,  and  then  melt  at  102.°  Ferric 
chloride  colours  the  aqueous  solution  greenish  brown. 

Triethylpyrogallolcarloxylic  acid,  C6H2(OC2H5)3C02H.  The 
ethyl  ether  of  this  substance  is  prepared  by  heating  the  preceding 
compound  with  caustic  potash,  ethyl  iodide  and  alcohol.  It  is 
an  odourless,  volatile  liquid,  which  is  readily  decomposed  by 
alcoholic  potash.1  The  free  acid  is  slightly  soluble  in  cold,  more 
readily  in  hot  water  and  alcohol,  and  crystallizes  in  long,  silky 
needles,  melting  at  100*5°.  It  was  first  obtained  from  triethyl- 
daphnetic  acid,  C6H2(OC2H5)3C2H2.C02H,  by  oxidation  with 
potassium  permanganate,  its  aldehyde  C6H2(OC2H5)3CHO,  being 
simultaneously  formed  as  an  oily  liquid  which  gradually  solidifies 
to  a  crystalline  mass  melting  at  70°.2 

1  Will  and  Albrecht,  Ber.  Deutsch.  Chem.  Ges.  xvii.  2100. 

2  Ber.  Deutsch.  Chem.  Ges.  xvii.  1087. 


380  AROMATIC  COMPOUNDS. 


PHLOROGLUCINOLCARBOXYLIC  ACID. 

This  acid  is  obtained  by  heating  phloroglucinol  with  acid  potas- 
sium carbonate  and  water  to  1300.1  It  crystallizes  in  needles, 
which  contain  a  molecule  of  water  and  are  only  slightly  soluble  in 
water,  more  readily  in  alcohol,  very  readily  in  ether  and  have  an 
acid  taste.  •  The  water  is  lost  at  100°,  carbon  dioxide  being  also 
slowly  evolved.  On  boiling  with  water  it  is  decomposed 
smoothly  into  phloroglucinol  and  carbon  dioxide.  Its  aqueous 
solution  is  coloured  an  intense  blue  by  ferric  chloride,  which 
soon  changes  to  dirty  brown,  and  its  alkaline  solution  turns 
brown  in  the  air. 

When  its  alcoholic  solution  is  saturated  with  hydrochloric 
acid,  carbon  dioxide  is  evolved  and  phloroglucinol  diethyl  ether 
is  formed  (Part  III.,  p.  187). 


HYDROXYQUINOLCARBOXYLIC  ACID. 

The  following  derivatives  of  this  acid  are  alone  known  : 

Triethylhydroxyquinolcarboxylic  acid,  C6H2(OC2H5)3C02H,  is 
formed  by  the  oxidation  of  the  two  isomeric  triethylaesculetic 
acids,  C6H2(OC2H5)3C2H2.CO2H,  with  potassium  permanganate, 
and  crystallizes  from  hot  water  in  fine  needles,  melting  at  134°. 
Its  aldehyde,  C6H2(OC2H5)3COH,  is  also  formed  and  crystallizes 
from  alcohol  in  splendid  pointed  prisms,  melting  at  95°. 

Trimethylhydroxyguinolcarboxylic  acid,  C6H2(OCH3)3C02H, 
resembles  the  ethyl  compound  and  melts  at  108° — 1090.2 

These  compounds  were  at  first  considered  as  derivatives  of 
phloroglucinolcarboxylic  acid.  When  the  triethylcompound  is 
distilled  with  lime,  however,  a  triethoxybenzene  is  obtained, 
which  melts  at  34°,  and  is  therefore  different  from  the  triethyl 
ether  of  pyrogallol  or  phloroglucinol,  so  that  it  must  be  that  of 
hydroxyquinol.3 

1  Bcr.  Deutsch.  Chem.  Ges.  xvii.  2103. 

2  Will,  ibid.  xvi.  2112. 

3  Will  and  Albrecht,  ibid.  xvii.  2108. 


QUINIC  ACID.  381 


CONSTITUTION    OF   THE   TRIHYDROXY- 
BENZOIC  ACIDS. 

According  to  theory,  six  of  these  compounds  can  exist,  but 
only  four  are  known  : 

Pyrogallolcarboxylic         Phloroglucinolcarboxylic 
Gallic  acid.  acid.  acid. 

C02H  C02H  CQ2H 


(  i      (  r      °T  r 

OH\  /OH              \/OH                      \/ 
OH                     OH                            OH 

Hydroxyquinolcarboxylic  acids. 

CO2H 
OH/\OH 

'\/OH 

C02H 

/\OH 
OH\/OH 

CO2H 

M°H 

OH 

The  constitution  of  gallic  acid  is  determined  by  its  formation 
from  bromoprotocatechuic  acid  and  a-bromoresorcylic  acid, 
whence  it  also  follows  that  pyrogallol  is  an  adjacent  trihydroxy- 
benzene,  and  that  in  phloroglucinol  the  hydroxyls  are  symmetri- 
cally arranged  (Part  III.,  p.  181).  The  latter  can  only  yield 
one  carboxylic  acid,  so  that  the  constitution  of  phloroglucinol- 
carboxylic  acid  is  determined ;  this  is  confirmed  by  its  formation 
from  daphnetic  acid,  in  which  a  hydroxyl  is  known  to  be  in  the 
ortho-position  to  the  carboxyl. 

The  constitution  of  the  hydroxyquinolcarboxylic  acid  from 
aesculetic  acid  has  not  yet  been  determined. 


QUINIC  ACID,  C0H7(OH)4C02H. 

2207  Count  Claude  de  la  Garaye,  in  1746,  obtained  a  crystal- 
line deposit l  from  the  extract  of  Peruvian  bark,  which  became 
known  as  Sel  essentiel  de  la  Garaye.  Hermbstiidt  of  Berlin 
showed  in  1785  that  this  "  Chinasalz  "  is  a  salt  of  lime,2  and 
Hofmann,  an  apothecary  of  Leer,  in  1790  detected  in  it  a 

1  Chimie  hydraulique,  Paris,  1746,  114.  2  Crell's  Ann.  ii.  115. 


382  AROMATIC  COMPOUNDS. 

characteristic  acid,  which  he  named  "  Chinasiiure,"  J  and  which 
was  carefully  investigated  by  Vauquelin  in  1806,  who  called  it 
acide  quinique?  Its  correct  formula  was  determined  by  Liebig  3 
and  Woskresensky.4 

It  occurs  to  the  amount  of  5 — 8  per  cent,  in  true  Peruvian 
bark,  combined  with  alkaloids  and  lime.  Stenhouse5  was  unable 
to  obtain  the  slightest  trace  from  the  false  China  nova  s.  surina- 
mensis  (Biwna  magnifolia) ;  but  Hlasiwetz  subsequently  showed 
that  it  is  present,  although  only  in  small  amount.6  Zwenger 
and  Siebert  have  also  detected  it  in  bilberry  leaves  (Vac- 
cinium  Myrtilhis),7  and  in  coffee  beans.8  They  obtained  an 
ounce  of  the  acid  from  some  baskets  of  bilberry  leaves  gathered 
in  May,  and  one  variety  of  Java  coffee  yielded  0*3  per  cent. 
Loew  discovered  it  in  meadow  hay,9  which  contains  about  0*6 
per  cent. 

Calcium  quinate  was  formerly  a  by-product  of  the  manufacture 
of  quinine,  but  is  not  obtained  by  the  method  now  in  use.10  It 
is  prepared  by  treating  the  powdered  bark  for  two  or  three  days 
with  cold  water,  adding  a  little  milk  of  lime  to  the  extract,  in 
order  to  precipitate  tanning  matters  and  the  small  quantity  of 
alkaloids  present,  and  evaporating  the  nitrate  until  it  has  the 
consistency  of  syrup.  The  calcium  quinate  which  separates  out 
after  some  weeks  is  purified  by  re -crystallization  and  decom- 
posed by  sulphuric  or  oxalic  acid. 

Quinic  acid  crystallizes  in  hard,  transparent,  monoclinic  prisms 
or  tablets,  has  a  very  sour  taste,  and  dissolves  at  9°  in  2-5  parts 
of  water,  more  readily  in  alcohol,  and  scarcely  at  all  in  ether. 
It  is  optically  active  and  its  aqueous  solution  is  laevorotatory. 

When  it  is  heated  it  melts  at  161'6°,n  and  loses  water  at  a 
higher  temperature,  forming  quinide,  C7H10O5,  which  separates 
from  water  in  crystals  resembling  those  of  salammoniac,  which 
have  an  acid  reaction  and  combine  with  bases  to  form  salts 
of  quinic  acid.12  It  probably  has  the  following  constitution, 
C6H7(OH)4CO.OC6H7(OH)3C02H. 

Quinic  acid  decomposes  on  dry  distillation  with  formation  of 
phenol,  quinol,  catechol,  ben  zoic  acid  and  other  products.13 

I  CrelVs  Ann.  ii.  314.  2  Ann.  Chim.  lix.  162. 
3  Ann.  Chcm.  Pharm.  vi.  14.               4  Ibid.  xxiv.  257. 

5  Ibid.  liv.  100.  «  Ibid.  Ixxix.  144. 

7  Ibid.  cxv.  108.  8  Ibid.  Suppl.  i.  77. 

9  Journ.  Prakt.  Chcm.  [2]  xix.  309.     10  Neues  Uandwdrtcrb.  ii.  532. 

II  Hesse,  Ann.  Chem.  Pharm.  cxiv.  292. 

12  Hesse,  ibid.  ex.  335.  13  Wohler,  ibid.  Ii.  146. 


QUINIC  ACID. 


When  lead  dioxide  is  added  to  its  aqueous  solution,  carbon 
dioxide  is  evolved  and  the  reaction  may  be  carried  on  by 
heating  the  mixture,  lead  quinate  and  quinol  being  formed  : 1 


C7H12Oe 

When  it  is  heated  with  manganese  dioxide  and  sulphuric 
acid,  quinone  is  formed,  while  protocatechuic  acid  may  be 
obtained  by  evaporating  a  solution  of  the  acid  to  which  bro- 
mine has  been  added,2  or  by  fusing  the  acid  with  caustic 
potash,3  or  caustic  soda,4  as  well  as,  together  with  a  large 
amount  of  benzoic  acid,  by  heating  quinic  acid  to  150°  with 
fuming  hydrochloric  acid.5 

Fuming  hydriodic  acid  reduces  it  at  120°  to  benzoic  acid  :6 

C7H1206+2HI  =  C7H602+4H20  +  I2. 

On  heating  with  concentrated  hydrochloric  acid  to  140° — 150°, 
parahydroxybenzoic  acid  and  quinol  are  formed ;  it  dissolves 
when  heated  with  sulphuric  acid  with  evolution  of  carbon  dioxide 
and  formation  of  quinoldisulphonic  acid  (Hesse).  Phosphorus 
chloride  converts  it  into  metachlorobenzoyl  chloride  (Grabe) : 

C7H1206  +  5PC15  =  C7H4C120  +  5POC13  +  8HC1. 

It  is  converted  by  the  animal  organism  into  hippuric  acid 
(Lautemann). 

The  whole  behaviour  of  quinic  acid  points  to  the  fact  that  it 
belongs  to  the  aromatic  addition-products.7  It  is  tetrahydroxy- 
hexhydrobenzoic  acid,  and,  since  it  is  optically  active,  must 
contain  an  asymmetric  carbon  atom,  so  that  it  has  the  following 
constitution : 

C02H 

CH 


H2Q       iCH.OH 


HO.HC,  XCH.OH 
;H 


1  Hesse,  Ann.  Chcm.  Pharni.  cxiv.  292.  2  Hesse,  ibid.  cc.  239. 

8  Grabe,  ibid,  cxxxviii.  203.  4  Hesse,  loc.  cit. 

6  Fittig  and  Hillebrand,  ibid,  cxciii.  197.  6  Ibid.  cxxv.  9. 

7  Grabe,  Ann.  Chem.  Pharm.  cxlvi.  66. 


384  AROMATIC  COMPOUNDS. 

It  differs  from  quercitol  (Part  III.  p.  194)  in  containing  a 
carboxyl  in  the  place  of  one  hydroxyl.  A  different  formula  has 
been  proposed  by  Lieben,  who  found  that  quinic  acid  yields 
iodoform  when  treated  with  iodine  and  caustic  potash ;  he 
therefore  assumes  that  its  constitution  must  be  expressed  by 
the  following  or  some  similar  formula  : l 

HO.CH        CH3 
HO.C  CH.OH 

HO.CH CH.CO2H. 

The  Quinates.  The  salts  of  quinic  acid  are  for  the  most  part 
readily  soluble  in  water,  slightly  in  alcohol,  and  crystallize  well. 
They  have  been  investigated  by  Baup,2  Woskrensky,  Hesse,  and 
Clemm.3 

Sodium  quinate,  C7Hn06Na  -f  2H2O,  crystallizes  in  large, 
nacreous,  rhombic  prisms. 

Clemm  was  unable  to  obtain  the  potassium  and  ammonium 
salts  in  crystals ;  their  solutions  only  gave  syrupy  residues  on 
evaporation  over  sulphuric  acid. 

Calcium  quinate,  (C7Hn06)2Ca  +  10H2O,  forms  silky,  rhombic 
plates,  or  long,  concentrically-grouped  prisms,  which  dissolve  at 
10°  in  6  parts  of  water  and  are  insoluble  in  absolute  alcohol. 

Barium  quinate,  (C7HnO6)2Ba+6H2O,  crystallizes,  according 
to  Henry  and  Plisson,  in  acute  octohedral  pyramids,  while  Baup 
always  obtained  it  in  dodecahedra  formed  by  the  combination  of 
two  pointed  pyramids,  and  Clemm  only  as  a  partially  crystalline 
mass. 

Lead  quinate,  (C7HnO6)2Pb,  crystallizes  in  readily  soluble 
needles ;  ammonia  added  to  its  solution  produces  a  voluminous, 
hydrated  precipitate  which  has  the  formula  C7H8O6Pb2,  after 
drying  at  200°. 

Silver  quinate,  C7HnO6Ag,  forms  warty  crystals,  which  readily 
dissolve  in  water  and  blacken  in  the  light. 

Copper  quinate,  (C7HnO6)2Cu  +  5H2O,  crystallizes  in  light 
blue  plates. 

Basic  copper  quinate,  C7Tl1()Q6Cu  +  2R2O,  is  obtained  by  boiling 
the  aqueous  solution  of  the  acid  with  an  excess  of  copper  oxide : 

1  Ann.  Chcm.  Pharm.  Suppl.  vii.  232. 

2  Ibid.  vi.  1  ;  Ann.  Chim.  Phys.  [2]  li.  56. 

3  Ann.  Chem.  Pharm.  ex.  345. 


ETHYL  QUINATE. 


385 


it  forms  small,  green  crystals,  which  are  only  slightly  soluble  in 
cold  water. 

Ethyl  quinate,  C6H7(OH)4C02.C2H5,  was  obtained  by  Hesse  by 
the  action  of  ethyl  iodide  on  the  silver  salt  ;  it  is  a  viscid  mass, 
which  is  readily  soluble  in  water  and  alcohol,  and  has  a  very 
bitter  taste. 

Ethyl  tetracetylquinate,  C6H7(OCO.CH3)4CO.OC2H5,  is  formed 
by  boiling  the  ethyl  ether  with  acetic  anhydride,  and  crystallizes 
from  boiling  water  in  plates ;  it  separates  from  ether  in  large, 
rhombic  crystals  which  melt  at  135°,  and  sublime  without 
decomposition  (Fittig  and  Hilldebrand). 


386  AROMATIC  COMPOUNDS. 


THE  XYLENE  GROUP. 

2208  It  has  been  already  mentioned  under  benzene  (Part  III. 
p.  66)  that  Mansfield  in  1848  discovered  that  coal-tar  naphtha 
contains,  besides  benzene,  its  homologues;  of  these  he  isolated 
the  following  (C  =  6) : 

Boiling-point. 

Toluol,  CUH8 about       113°. 

Cumol,  C18H12 143°— 145°. 

Cymol,  C20H14 170°— 172°. 

He  adds,  it  is  interesting  to  note,  "that  tar-oil  contains 
among  its  constituents  the  only  four  known  members  of  the 
series  C6-f-n(C2H9).  It  seems,  therefore,  not  improbable  that 
the  gap  which  still  exists  in  this  series  (n  =  5),  corresponding  to 
a  substance  whose  boiling-point  lies  between  those  of  toluol 
and  cumol,  will  be  filled  by  a  compound  to  be  obtained  from 
tar-oil.1 

Soon  after  this,  Cahours  discovered  xylol  (icy&ne),C8H10(C  =  12), 
boiling  at  128° — 130°,  along  with  toluol  in  crude  wood-spirit 
(£v\ov,  wood),2  and  Volkel  found  the  same  hydrocarbons  in 
wood-tar.3  Church  then  stated  that  xylol  is  also  contained 
in  coal-tar  oil,  and  boils  at  126'2°,4  whereas  Ritthausen5  and 
Hiltenkamp 6  could  only  detect  in  it  the  hydrocarbons  already 
discovered  by  Mansfield. 

Warren  de  la  Itue  and  H.  Miiller  then  showed  that  Rangoon 
tar  contains  benzol  and  its  homologues,  which  they  were 
unable  to  isolate,  but  recognised  by  conversion  into  their 
characteristic  nitro-compounds.7  Shortly  before  this  time, 
Bussenius  and  Eisenstuck  had  investigated  the  rock  oil  from 

1  Ann.  Chem.  Pharm.  Ixix.  162.  2  Ibid.  Ixxiv.  168  ;  Ixxvi.  286. 

8  Ibid.  Ixxxvi.  331.  4  Phil.  Mag.  [4]  ix.  256. 

8  Journ.  Prakt.  Chem.  Ixi.  74.  «  Ann.  Chem.  Pharm.  xcv.  89. 
7  Journ.  Prakt.  Chem.  Ixx.  300. 


THE  XYLENE  GROUP.  387 

Sehnde  in  Hanover,  and  discovered  in  it  a  new  hydrocarbon, 
which  they  called  petrol,  C8H10,  its  existence  being  proved  by  its 
characteristic  trinitro-derivative;1  and  Hugo  Miiller  then  showed 
that  the  hydrocarbon  obtained  from  coal-tar  and  boiling  at  140° 
is  not  cumol,  but  xylol,  which  also  occurs  in  the  oils  from 
Burmah  and  Sehnde,  trinitropetrol  being  identical  with  trinitro- 
xylol.2  In  spite  of  this  Bechamp  repeated  the  statement  that 
xylol  boils  at  126° — 130°,  adding  that  coal-tar  also  contains  a 
"new"  hydrocarbon  boiling  at  139°— 140°.3 

Mansfield's  cumol  was  subsequently  proved  to  be  a  mixture 
of  trimethylbenzenes. 

After  Fittig  and  Tollens  had  made  the  important  discovery 
that  the  synthetic  methylphenyl  or  methylbenzol  is  identical  with 
toluol,4  it  was  supposed  that  ethylphenyl  or  ethylbenzol  would 
be  identical  with  xylol.  This,  however,  was  found  not  to  be 
the  case,  since  it  boils  as  much  as  7°  lower  than  the  latter,  and 
does  not  yield  a  crystallized  trinitro-derivative. 

Beilstein  then  investigated  xylol  more  carefully ;  he  fully  con- 
firmed Mliller's  observations  and  found  that  on  oxidation  with 
chromic  acid  it  yields  dibasic  terephthalic  acid,  C8H6O4.5  About 
this  time  Fittig  prepared  methylbenzyl,  which  he  considered  to 
be  identical  with  xylol,  by  the  action  of  sodium  on  a  mixture 
of  bromotoluol  and  methyl  iodide.6  He  also  found  that  ethyl- 
phenyl is  easily  oxidized  to  benzoic  acid  and  that  its  derivatives 
are  completely  different  from  those  of  xylol.7 

Glinzer  and  Fittig  then  undertook  a  careful  examination  of 
methylbenzyl,  or,  as  they  now  termed  jt,  methyltoluol ;  like 
xylol  it  yielded  terephthalic  acid  on  oxidation,  but  the  trinitro- 
derivatives  proved  to  have  different  properties.8  A  further 
investigation  of  the  oxidation  products  of  xylol  showed  that 
toluic  acid,  the  next  homologue  of  benzoic  acid,9  is  first  formed, 
and  this  was  also  obtained  from  methyltoluol.  In  spite  of  this, 
however,  the  hydrocarbons  were  shown  to  be  different,  as  the 
properties  of  their  substitution  products  did  not  agree.10 

Fittig  and  Velguth  then  obtained  a  third  isomeric  hydrocarbon, 
which  they  named  isoxylol,  by  heating  monobasic  mesitylenic 
acid,  C6H3(CH3)2CO2H,  prepared  by  the  oxidation  of  mesitylene, 

1  Ann.  Chem.  Pharm.  cxiii.  151.         2  Zeitschr.  Chcm.  1864,  161. 
3  Compt.  Rend.  lix.  47.  4  Ann.  Chem.  Pharm.  cxxxi.  303. 

5  Ibid,  cxxxiii.  32.  6  Ibid,  cxxxiii.  47. 

7  Ibid,  cxxxiii.  222.  8  Ibid,  cxxxvi.  303. 

9  Yssel  de  Schepper  and  Beilstein,  ibid,  cxxxvii.  301. 
10  Fittig,  Ahreus  and  Mattheides,  ibid,  cxlvii.  15. 


AROMATIC  COMPOUNDS. 


C6H3(CH3)3,  with  lime.  The  substitution  products  of  this  body 
agreed  so  exactly  with  those  of  xylol,  that  the  two  hydro- 
carbons would  have  been  considered  identical  had  not  their 
oxidation  products  been  completely  different.  Isoxylol  was  not 
attacked  by  dilute  nitric  acid,  while  chromic  acid  oxidized  it  to 
isophthalic  acid,  the  isomeride  of  terephthalic  acid.1 

Fittig  soon  found  a  very  simple  explanation  of  this  exceptional 
and  almost  incredible  fact.  Xylol  proved  to  be  a  mixture  of 
methyltoluol  or  paraxylol  with  isoxylol,  or,  as  it  is  now  termed, 
metaxylol.  Beilstein,  who  had  looked  upon  it  as  a  chemical 
individual,  had  only  obtained  in  a  pure  state  the  difficultly 
soluble  substitution  products  of  metaxylol  and  the  oxidation  pro- 
ducts of  paraxylol,  which  are  most  readily  formed.2  The  third 
isomeric  dimethylbenzene,  orthoxylol  was  then  prepared  syn- 
thetically and  subsequently  discovered  in  coal-tar  by  Jacobsen.3 

According  to  Fittig,  coal-tar  naphtha  contains  a  preponde- 
rating amount  of  metaxylene,  while  Jacobsen  found  20 — 25  per 
cent,  of  orthoxylene,  and  10—15  per  cent,  of  paraxylene  in  a 
series  of  samples  of  xylene. 

In  order  to  separate  these,  the  coal-tar  xylene,  boiling  at 
about  140°,  is  repeatedly  shaken  up  with  ordinary  concentrated 
sulphuric  acid,  the  ortho-  and  meta-compounds  alone  being 
dissolved.  The  solution  is  diluted  with  water  and  neutralized 
with  chalk,  the  filtrate  being  then  treated  with  a  slight  excess 
of  sodium  carbonate  and  concentrated  by  evaporation.  The 
sodium  orthoxylenesulphonate  separates  out  on  cooling  in  large 
prisms,  which  can  readily  be  purified  by  re-crystallization. 
An  additional  crop  of  this  salt  can  be  obtained  by  further  eva- 
poration, while  the  meta-salt  remains  in  solution.  The  pure 
hydrocarbons  are  then  obtained  by  heating  the  salts  with 
concentrated  hydrochloric  acid. 

The  portion  of  the  crude  xylene  which  does  not  dissolve  in 
ordinary  sulphuric  is  agitated  with  the  slightly  fuming  acid, 
the  mixture  being  gently  heated ;  the  paraffins  are  thus  left 
undissolved,  while  paraxylenesulphonic  acid  is  formed,  which 
is  only  slightly  soluble  in  dilute  sulphuric  acid,  and  is  purified 
by  re-crystallization  (Jacobsen),  the  hydrocarbon  being  then 
obtained,  as  before,  by  the  action  of  hydrochloric  acid. 

The  meta-compourid  alone  may  be  extracted  from  crude 
xylene  by  boiling  it  for  a  considerable  time  with  a  mixture  of 

1  Ann.  Chem.  Pharm.  cxlviii.  1.  2  Ibid.  clui.  265. 

3  Ber.  Deutsch.  Clwrn.   Ges.  x.  1010. 


THE  XYLENES.  -        389 


one  volume  of  concentrated  nitric  acid  and  two  or  three  volumes 
of  water,  the  ortho-  and  para-compounds  being  thus  oxidized  to 
the  corresponding  toluic  acids,  C6H4(CH3)CO2H,  or  their  nitro- 
derivatives,  while  the  meta- compound  is  scarcely  attacked. 
When  the  evolution  of  red  fumes  ceases,  the  liquid  is  distilled 
with  steam  and  the  distillate  agitated  with  caustic  soda,  washed 
with  water,  dried  and  distilled.1 

In  order  to  estimate  the  amounts  of  the  three  isomerides 
quantitatively,  100  c.c.  of  the  crude  xylene  are  boiled  for  half 
an  hour  to  an  hour  with  a  mixture  of  40  c.c.  of  nitric  acid 
of  sp.  gr.  1'4  and  60  c.c.  of  water,  the  whole  being  repeatedly 
agitated.  The  unattacked  portion  is  then  washed  with  caustic 
soda  and  distilled  with  steam,  the  distillate  is  measured  and 
shaken  up  with  1*5  vols.  of  concentrated  sulphuric  acid,  the 
metaxylene  being  thus  dissolved,  while  the  paraffins  remain 
behind  and  are  measured  in  a  graduated  cylinder. 

The  amount  of  paraxylene  is  found  by  thoroughly  agitating 
100  c.c.  of  the  crude  xylene  with-  120  c.c.  of  concentrated  sul- 
phuric acid  for  half  an  hour,  a  mixture  of  paraffins  and  para- 
xylene being  left  undissolved  ;  this  is  then  treated  with  an 
equal  volume  of  fuming  sulphuric  acid,  containing  20  per  cent, 
of  trioxide,  which  dissolves  out  the  paraxylene.  The  amounts 
of  paraxylene,  metaxylene  and  paraffins  are  thus  directly 
measured,  the  difference  from  100  c.c.  being  that  of  the 
orthoxylene. 

In  this  way  Levinstein  has  found  in  various  samples  of  crude 
English  and  Scotch  xylene  : 2 

Paraxylene    . 3 — 10  percent. 

Metaxylene 70—87 

Orthoxylene 2—15 

Paraffins 3—10 

According  to  Reuter  these  methods  of  separation  are  not  accurate, 
since  nitric  acid  of  the  concentration  employed  also  attacks 
metaxylene,  and  paraxylene  dissolves  in  ordinary  sulphuric  acid^ 
although  to  a  much  smaller  extent  than  its  isomerides.  The 
resistance  of  the  xylenes  to  the  action  of  acids  is,  however, 
considerably  increased  by  the  presence  of  paraffins.3 

1  Fittig  and  Velguth,  Ann.  Chem.  Pharm.   cxlviii.  10  ;  Tawildarow,  Zcitschr. 
Chem.  1870,  418  ;  Bruckner,  Ber.   Deutsch.   Chem.  Ges.  ix.  405. 

2  Ibid.  xvii.  444.  3  Ibid.  xvii.  2028. 

256 


390      -  AROMATIC  COMPOUNDS. 

When  a  mixture  of  the  three  xylenes  is  treated  with  bromine 
containing  1  per  cent,  of  iodine,  they  are  converted  into  the  tetra- 
bromoxylenes,  C6Br4(CH3)2,  which  yield  the  tetrabromophthalic 
acids  quantitatively  when  heated  with  bromine  and  water  to 
160°— 170°: 

C6Br4(CH3)2 + 6Br2  +  4H20  =  C6Br4(C02H)2 + 1 2HBr. 

Since  these  can  readily  be  separated,  the  composition  of  the 
original  mixture  can  be  determined  in  this  way.1 


THE  XYLENES,  OR  DIMETHYLBENZENES, 


2209  Orthoxylene,  (1  :  2),  was  first  prepared  pure  by  the  dis- 
tillation of  paraxylic  acid,  C6H3(CH3)2CO2H,  with  lime  ;  2  it  is 
also  formed  by  the  action  of  sodium  on  a  mixture  of  ortho- 
bromotoluene  and  methyl  iodide,3  and  when  a  hot  mixture  of 
toluene  and  aluminium  chloride  is  treated  with  methyl  chloride. 
A  small  quantity  of  paraxylene  is  always  formed  in  this  reaction, 
together  with  still  less  metaxylene  and  a  larger  amount  of 
the  isomeric  trimethylbenzenes.4  It  has  also  been  prepared 
from  cantharidin,  C10H12O4,  which  is  the  characteristic  con- 
stituent of  Spanish  flies,  and  yields  pure  orthoxylene  when 
heated  with  phosphorus  pentasulphide.5 

It  is  a  liquid  which  boils  at  142°  —  143°,  solidifies  in  a  freezing 
mixture  to  crystals,  melting  at  —  28°,6  and  is  oxidized  to  ortho- 
toluic  acid  by  heating  with  dilute  nitric  acid,  while  chromic 
acid  produces  complete  combustion.  When  agitated  with  a 
boiling  solution  of  potassium  permanganate,  however,  it  yields 
phthalic  acid.7  A  cold  mixture  of  nitric  and  sulphuric  acids 
converts  it  into  liquid  nitro-derivatives,  and  a  single  drop  of 
orthoxylene  can  thus  be  distinguished  from  the  para-  and 
meta-compounds.8 

1  Friedel  and  Crafts,  Compt.  rend.  ci.  1218. 

2  Bieber  and  Fittig,  Ann.  Chem.  Pharm.  clvi.  238. 

3  HiibnerandJannasch,  ibid.  clxx.  117  ;  Reymann,  Bull.  Soc.  Chim.  xxvi.  582. 

4  Jacobsen,  Bcr.  Dcutsch.  Chcm.  Ges.  xiv.  2624. 

5  Piccard,  ibid.  xii.  580. 

6  Colson,  Ann.  Chim.  Phys.  [6]  vi.  128. 

7  Clans  and  Pieszcek,  Be.r.  Deutsch.  Chem.  Ges.  xix.  3083. 

8  Jacobsen,  ibid.  xix.  2518. 


ORTHOXYLENE.  391 


Dihydro-orthoxyhne,  or  Cantharcne,  C6H6(CH3)2.  The  com- 
pound C10H13I9jO3  is  formed  by  the  action  of  hydriodic  acid  on 
cantharidin,  and  is  converted  into  cantharene  by  heating  with 
concentrated  caustic  potash;  the  latter  boils  at  134°,  smells  like 
camphor  and  oil  of  turpentine,  rapidly  absorbs  oxygen  from  the 
air  and  is  oxidized  to  orthotoluic  acid  by  dilute  nitric  acid.1 

Metaxylene  (1 :  3)  may  be  obtained  pure  by  heating  xylic  acid 
C6H3(CH3)2C02H  (Bieber  and  Fittig),  or  the  isomeric  mesity- 
lenic  acid  (Fittig  and  Velguth)  with  lime,  and  by  the  action  of 
sodium  on  a  mixture  of  methyl  iodide  and  meta-iodotoluene.2 
It  boils  at  139'8°  and  has  a  specific  gravity  of  0*8780  at  0°,  and  of 
0'8660  at  15°;  it  solidifies  when  strongly  cooled  and  then  melts 
at  —  54°  to  —  53°.3  It  is  only  attacked  with  difficulty  by  dilute 
nitric  acid,  even  on  boiling ;  when,  however,  it  is  boiled  for 
several  hours  with  nitric  acid  of  specific  gravity  1'4,  diluted 
with  one  and  a  half  times  its  volume  of  water,  metatoluic  acid  is 
obtained  (Reuter),  while  chromic  acid  solution  oxidizes  it  to 
isophthalic  acid,  which  is  also  formed,  together  with  metatoluic 
acid,  by  the  action  of  potassium  permanganate.4 

Metaxylene,  as  already  mentioned,  occurs  in  various  tars  and 
petroleums,  and  it  has  also  been  found  in  that  from  the 
Caucasus.5  It  forms  a  characteristic  trinitro-derivative,  which  is 
only  slightly  soluble  in  alcohol  and  yields  nitrodiamidometaxy- 
lene  (p.  409)  on  partial  reduction.  These  reactions  serve  to 
detect  small  quantities  of  metaxylene  in  petroleum,  &c. 

Tetrahydrometaxylene,  C6H8(CH3)2,  is  formed  when  camphoric 
acid,  C8H14(C02H)2,  is  heated  to  200°  with  concentrated  hydriodic 
acid,6  and  has  also  been  prepared  from  oxycamphoric  acid,  under 
which  it  will  be  mentioned.  It  is  a  liquid  which  boils  at  119°, 
and  is  converted  into  trinitrometaxylene  by  a  mixture  of  nitric 
and  sulphuric  acids. 

Hexhydrometaxylene,  C6H10(CH3)2,  is  obtained  by  heating 
camphoric  acid  or  metaxylene  with  hydriodic  acid  to  280°.  It 
occurs  in  Baku  petroleum  (Beilstein  and  Kurbatow)  and  in 
essence  of  resin  (Renard)  ;  it  boils  at  116° — 120°,  and  also  yields 
trinitrometaxylene  with  nitric  and  sulphuric  acids.7 

ParaxyUne  (1 : 4)  is  formed  by  the  action  of   sodium  on  a 

1  Piccard,  Ber.  Deutsch.   Chem.  Ges.  xix.  1406. 

2  Wroblewsky,  Ann.  Chem.  Pharm.  cxcii.  200.  3  Colson,  loc.  cit. 

4  Glaus  and  Burstert,  JBcr.  Deutsch.  Chem.  Ges.  xix.  3084. 

5  Doroschenko,  xviii.  Ref.  662  :  Markownikow,   Ann.  Chem.  Pharm.  ccxxxiv. 
89. 

6  Wreden,  Ann.  Chem.  Pharm.  clxxxvii.  171.  7  Ibid,  clxxxvii.  151. 


AROMATIC  COMPOUNDS. 


mixture  of  methyl  iodide  and  parabromotoluene l  or  paradi- 
bromobenzene.2  It  boils  at  136° — 137°,  and  has  a  specific  gravity 
of  0'8621  at!9'5°;  when  strongly  cooled  it  solidifies  to  rhombic 
prisms  resembling  heavy  spar,3  which  melt  at  +  15°.  Dilute 
nitric  acid  oxidizes  it  to  paratoluic  acid,  while  chromic  acid  or 
potassium  permanganate  give  terephthalic  acid. 

Paraxylene  occurs  in  the  petroleum  from  Galicia  along  with 
metaxylene.4 

Hcxhydroparaxylene,  C6H10(CH3)2,  is  obtained  by  heating  mono- 
bromocamphor,  C10H15BrO,  with  zinc  chloride  to  150° — 160°,  and 
is  a  liquid  boiling  at  157 '6°,  which  is  converted  into  trinitropara- 
xylene  by  nitric  and  sulphuric  acids.5 


SUBSTITUTION  PRODUCTS  OF  THE  XYLENES. 

22 10  When  one  atom  of  hydrogen  is  replaced  in  the  aromatic 
nucleus,  six  isomeric  compounds  may  be  formed.  Metaxylene 
yields  three,  which  are  distinguished  as  symmetric  =  s,  asym- 
metric =  a,  and  adjacent  (vicinus)  —  v.  Two,  asymmetric  =  a, 
and  adjacent  =  v,  are  derived  from  orthoxylene,  while  paraxylene 
only  yields  one,  which  has  therefore  received  no  more  particular 
designation. 


HALOGEN  SUBSTITUTION  PRODUCTS  OF  THE 

XYLENES. 

v-CUor orthoxylene,  C6H3(CH3)2C1(1 : 2  :  3),  is  formed,  together 
with  the  following  compound,  when  orthoxylene,  to  which  5  per 
cent,  of  iodine  has  been  added,  is  treated  with  chlorine  at  0°.  In 
order  to  separate  the  two  isomerides,  they  are  converted  into  the 
sulphonic  acids,  the  pure  sodium  salts  of  which  are  then 
decomposed  by  heating  with  concentrated  hydrochloric  acid. 
Adjacent  chlor orthoxylene  is  a  liquid  boiling  at  189'5°. 

a-Chlororthoxylene  (1:2:4)  boils  at  191'5°  and,  like  its 
isomeride,  remains  liquid  at  —  20°.6 

1  Fittig  and  Glinzer,  Ann.  Chcm.  Pharm.  cxxxvi.  303. 

2  V.  Meyer,  Ber.  Dcutsch.  Chem.  Ges.  iii.  753  ;  Jannasch,  ibid.  x.  1356. 

3  Jacobsen,  ibid.  xvii.  2379.  4  Palewski,  ibid,  xviii.  1915. 
6  R.  Schiff,  ibid.  xiii.  1408.                           6  Kriiger,  ibid,  xviii.  1755. 


XYLENE  SUBSTITUTION-PRODUCTS.  393 

The  chlororthoxylenes  are  converted  by  oxidation  into  the 
corresponding  chlorotoluic  and  chlorophthalic  acids. 

According  to  Glaus  and  Kautz,  only  one  chlororthoxylene  is 
formed,  which  boils  at  205°  and  yields  the  following  compounds 
on  further  chlorination : x 

Melting-       Boiling- 
Dichlororthoxylene,  C6H2C12(CH3)2,  point.         point. 

crystalline  mass  .  .  .  +  3°  227° 

Trichlororthoxylene,  C6HC13(CH3)2, 

lustrous  needles  ....  93°  265° 
Tetrachlororthoxylene,  C6C14(CH3)2, 

long  needles 215° 

a- Chlorometaxylene,  C6H3(CH3)2C1(1 :  3  : 4),  is  formed  when 
letaxylene  is  chlorinated  at  0°  in  presence  of  iodine ;  the  crude 
luct,  which  distils  between  185° — 188°,  is  purified  by  con- 
certing it  into  the  sulphonic  acid  and  then  preparing  the  sodium 
salt  or  chlorometaxylenesulphamide,  C6H2(SO2.NH2)C1(CH3)2, 
from  this.  The  latter  crystallizes  from  hot  alcohol  in  hard,  com- 
pact, lustrous  prisms  melting  at  195°.  Both  of  these  compounds 
yield  pure  chlorometaxylene  when  heated  with  hydrochloric  acid. 
It  boils  at  186*5°  and  does  not  solidify  at  -  20° ;  it  is  oxidized  to 
chlorometatoluic  acid  by  chromic  acid,  while  it  is  converted 
into  ortho-horn oparahydroxybenzoic  acid  by  fusion  with  caustic 
potash.2 

Chloroparaxylene,  C6H3(CH3)2C1(1  :  4 :  2),  is  obtained  in  a 
precisely  similar  manner  to  chlorometaxylene  ;  it  boils  at  186° 
and  solidifies  in  a  freezing  mixture  to  a  crystalline  mass,  which 
melts  at  +  2°. 

Dichloroparaxylene,  C6H2(CH3)2C12,  is  only  slightly  soluble  in 
cold,  readily  in  hot  alcohol,  and  crystallizes  in  flat  needles  or 
plates  ;  it  melts  at  71°  and  boils  at  2210.3 

a-Bromorthoxylene,  C6H3(CH3)2Br(l  :  2  : 4),  is  formed  by  the 
direct  bromination  of  orthoxylene  in  the  cold  in  the  presence  of 
iodine,  no  isomeride  being  produced,4  and  more  slowly  when 
bromine  alone  is  allowed  to  act  in  the  dark,  orthoxylyl  bromide 
being  obtained  in  the  sunlight5  It  boils  at  214'5°  and  solidifies 
below  0°  to  a  fibrous,  crystalline  mass,  melting  at  —  0'2°.  When 
heated  with  ethyl  chloroformate  and  sodium  amalgam,  paraxylic 
acid,  C6H3(CH3)2CO2H,  is  formed. 

1  Jacobsen,  Ber.  Dcutsch.  Chem.  Ges.  xviii.  1367. 

2  Ibid,  xviii.  1760.  3  Kluge,  ibid,  xviii.  2098. 

4  Jacobsen,  ibid.  xvii.  2372.  5  Schramra,  ibid,  xviii.  1278. 


AROMATIC  COMPOUNDS. 


The  following  compounds  are  formed  by  the  further  action  of 
bromine  (Jacobsen) : 

Solid dilromorthoxylene,C6R2(CH3)2Br2(l :  2  : 4  :  5), crystallizes 
from  hot  alcohol  in  large,  rhombic  plates,  which  melt  at  88° ;  it 
readily  sublimes  in  very  large,  thin  plates,  boils  at  278°  and  yields 
symmetric  tetramethylbenzene,  C6H2(CH3)4,  on  treatment  with 
sodium  and  methyl  iodide. 

Liquid  dibromorihoxylene  boils  at  277°  and  solidifies  in  the 
cold  to  a  hard  crystalline  mass,  melting  at  +  6'8°. 

Tctrdbromorthoxylene,  C6(CH3)2Br4,  is  formed  when  orthoxylene 
is  allowed  to  drop  into  bromine  containing  1  per  cent,  of  alumi- 
nium bromide,  the  whole  being  kept  at  O0.1  It  is  very  slightly 
soluble  in  alcohol,  readily  in  benzene,  and  crystallizes  in  long, 
lustrous  needles,  which  melt  at  262°,  or  according  to  Bliimlein  at 
254°— 255°,  and  boil  at  374°— 375°. 

Jacobsen  was  unable  to  prepare  tribromorthoxylene  pure. 

a-Bromometaxylene,  C6H3(CH3)2Br  (1:3:4),  is  prepared  like 
the  ortho-compound ;  it  is  a  liquid,  which  boils  at  203° — 204°, 
and  is  converted  into  the  corresponding  bromotoluic  acid  by  oxi- 
dation,2 while  xylic  acid  is  formed  by  the  action  of  carbon 
dioxide  and  sodium.3 

s-Bromometaxylene,  (1:3: 5),  has  been  prepared  from  bromi- 
nated  metaxylidine  by  the  diazo-reaction.  It  boils  at  204°, 
remains  liquid  at  —20°,  and  is  converted  into  symmetric 
dimethylethylbenzene  by  sodium  and  ethyl  bromide.4 

a-Dilromometaxylene,  C6H2(CH3)2Br2,  is  formed  when  meta- 
xylene  is  allpwed  to  stand  in  contact  with  an  excess  of  bromine 
for  twenty-four  hours,  the  liquid  being  kept  cool.5  It  crystallizes 
from  alcohol  in  colourless,  nacreous  plates,  boils  at  255° — 256°, 
and  melts  at  72°.6 

f3-Dibromometaxylene  was  obtained  by  Wroblewsky,  together 
with  his  monobromoxylene,  as  a  liquid  which  boils  at  252°  and 
does  not  solidify  at  —20°. 

Tetrabromometaxylene,  C6(CH3)2Br4,  is  formed  when  meta- 
xylene  is  allowed  to  stand  for  a  long  time  in  contact  with 
a  large  excess  of  bromine.  It  is  scarcely  soluble  in  cold, 
slightly  in  boiling  alcohol,  but  dissolves  readily  in  benzene, 

1  Bliimlein,  Ber.  Deutsch.  Chcm.  Gcs.  xvii.  2492. 

2  Fittig,  Ann.  Chcm.  Pharm.  cxlvii.  31. 

3  Kekule,  ibid,  cxxxvii.  186. 

4  Wroblewsky,  ibid,  cxcii.  115. 

5  Fittig,  Ahrens  and  Mattheides,  ibid,  cxlvii.  24, 

6  Fittig  and  Bieber,  ibid.  clvi.  236. 


NITRO-ORTHOXYLENES.  395 

and  crystallizes  in  fine  needles  which  melt  at  241°  (Fittig 
and  Bieber). 

Bromoparaxyhne,  C6H3(CH3)2Br  (1:4:  2),  is  prepared  by  the 
action  of  bromine  on  cooled  paraxylene  in  the  presence  of  iodine, 
and  is  also  formed  when  bromine  is  allowed  to  act  alone  in  the 
dark  (Schramm).  It  is  a  liquid,  which  boils  at  205'5°,  and  some- 
times solidifies  when  strongly  cooled,  but  frequently  remains 
liquid  until  a  crystal  of  the  solid  compound  has  been  added,  when 
it  forms  plates  or  tablets,  melting  at  +  9°.1 

Dibromoparaxylene,  C6H2(CH3)2Br2  (1:4:2:  5),  boils  at  261°, 
and  crystallizes  from  alcohol  in  large  plates  or  flat  needles, 
melting  at  75*5°.  When  these  are  allowed  to  remain  in  the 
mother  liquor  they  are  converted  into  transparent,  asymmetric 
crystals,  which  closely  resemble  regular  octohedra  (Jacobsen). 
It  is  converted  into  symmetric  tetramethylbenzene  by  the  action 
of  sodium  and  methyl  iodide.2 

In  addition  to  this  compound,  a  liquid  dibromoparaxylene, 
which  boils  at  260° — 264°  and  solidifies  in  a  freezing  mixture, 
is  formed  in  small  quantity. 

A  tribromoparaxylene  was  not  formed  when  the  necessary 
quantity  of  bromine  was  added,  the  following  substance  being 
obtained  together  with  the  preceding  compounds  : 

Tetrabromoparaxylene,  C6(CH3)2Br4,  is  very  slightly  soluble  in 
alcohol,  and  crystallizes  from  hot  toluene  in  long,  fine  needles, 
melting  at  253°. 


NITRO-SUBSTITUTION   PRODUCTS   OF   THE 
XYLENES. 

2211  v-Nitro-ortJwxylene,  C6H3(CH3)2N02  (1:2:  3),  is  formed, 
together  with  the  following  compound,  when  orthoxylene  is 
treated  in  a  freezing  mixture  with  concentrated  nitric  and 
sulphuric  acids  ;  it  is  a  liquid,  which  boils  at  245°  —  2470.3 

a-Nitro-orthoxylene  (1:2:  4)  is  almost  the  sole  product  when 
pure  nitric  acid  is  employed  ;  it  crystallizes  from  alcohol  in  long, 
brittle,  light  yellow,  lustrous  prisms,  melts  at  290°  and  boils  at 
2800.4 


1  Jannasch,   Ann.    Chcm.   Pharm.   clxxi.   82  ;  Jacobsen,  Ber.  Dcutsch.  Chem. 
Ges.  xviii.  356.  2  Jannasch,  ibid.  x.  1357. 

3  Nolting  and  Forel,  ibid,  xviii.  2669.  4  Ibid.  xvii.  159. 


396  AROMATIC  COMPOUNDS. 

Zkrtitro-orthoxylene,  C6H2(CH3)2(N02)2,  is  formed,  together 
with  the  following  compound  when  orthoxylene  is  heated  for 
a  considerable  time  to  100°  with  a  mixture  of -nitric  and  sul- 
phuric acids.  It  crystallizes  from  boiling  alcohol  in  long,  lustrous 
needles,  melting  at  71°. 

Trinitro-orthoxylene,  C6H(CH3)2(NO2)3,  forms  white,  lustrous 
scales,  which  melt  at  178°,  and  are  almost  insoluble  in 
alcohol.1 

v-Nitrometaxylene  (1  : 3  :  2)  is  obtained  by  the  action  of  nitric 
and  sulphuric  acids  on  metaxylene  in  the  cold.2  It  has  been 
prepared  pure  from  the  corresponding  nitrometaxylidine  by  the 
diazo-reaction.3  It  is  a  liquid  boiling  at  225°. 

a-Nitrometaxylene  (1:3:  4)  is  formed  in  the  preparation  of 
the  preceding  compound,  and  in  preponderating  amount  when 
pure,  well-cooled  nitric  acid  is  employed.  It  is  a  light  yellow 
liquid,  which  boils  at  238°  and  does  not  solidify  at  -  20°.4 

s-Nitrometaxylene  (1:3:5)  is  obtained  from  nitro-a-metaxy- 
lidine  by  dissolving  it  in  absolute  alcohol,  adding  two  molecules 
of  sulphuric  acid,  and  then  treating  the  well-cooled  liquid  with 
twice  the  theoretical  quantity  of  ethyl  nitrite  in  order  to  prevent 
the  formation  of  the  diazo-amido-compound.  The  liquid  is 
heated  to  boiling  after  standing  for  some  time,  the  alcohol  driven 
off  and  the  remainder  distilled  with  steam. 

s-Nitrometaxylene  boils  at  263°,  and  crystallizes  from  alcohol 
in  large,  flat  needles,  melting  at  74° — 75°.5 

s-Dinitrometaxylene,  C6H2(CH3)2(NO2)2  (1 : 3  : 4  : 6),  is  readily 
prepared  by  heating  metaxylene  with  fuming  nitric  acid;  it 
crystallizes  from  hot  alcohol  in  large,  flat,  colourless  needles  or 
lustrous  prisms,  melting  at  93°.6 

v-Dinitrometaxylene  (1  :  3  :  4 :  2)  is  formed  together  with .  its 
isomerides  when  xylene  is  nitrated  at  a  low  temperature  with 
a  mixture  of  nitric  and  sulphuric  acids ;  it  is  readily  soluble  in 
alcohol,  and  crystallizes  in  scale-like  plates,  melting  at  83°.7 

Trinitrometaxylene,  C6H(CH3)2(NO2)3  (1:3:2:4:6).  This 
characteristic  compound,  which  has  been  previously  mentioned 

1  Drossbach,  Ber.  Deutsch.  Chem.  Gcs.  xix.  2156. 

2  Noltiug  and  Forel,  Ber.  Deutsch.  Chem.  Gcs.  xviii.  2668. 

3  Grevingk,  ibid.  xvii.  2430. 

4  Tawildarow,  Zeitschr.  Chem.  1870,  418  ;  Harmsen,  Ber,  Deutsch.  Chem.  Ges. 
xiii.  1558. 

5  Wroblewsky,  Ann.  Chem.  Pharm.  ccvii.  91 ;  Thb'l,  Ber.  Deutsch.  Chem.  Ges. 
xviii.  359  ;  Nblting  and  Forel. 

0  Fittig,  Ann.  Chem.  Pharm.  cxlvii.  16  ;  cxlviii.  5. 
7  Grevingk,  Ber.  Deuttsch.  Chem.  Gcs.  xvii.  2422. 


NITROXYLENES.  397 


(p.  387),  is  formed  when  metaxylene  or  the  preceding  compounds 
are  heated  with  a  mixture  of  nitric  and  sulphuric  acids.  It 
is  scarcely  soluble  in  cold,  very  slightly  in  boiling  alcohol, 
and  crystallizes  in  fine,  flat,  colourless  needles,  melting  at 
1760.1  ^ 

Nitroparaxylcne,  C6H3(CH3)2N02,  is  obtained  by  allowing  the 
calculated  quantity  of  fuming  nitric  acid  to  drop  into  well-cooled 
paraxylene.  It  is  a  yellow  liquid,  which  boils  at  239°  and  does 
not  solidfy  at  -  20°.2 

a-Dinitroparaxylene,  C6H2(CH3)2(N02)2  (1  :  4  : 2  : 6),  is  formed, 
together  with  its  isomerides,  when  paraxylene  is  dissolved  in 
cold,  fuming  nitric  acid.  It  crystallizes  from  alcohol  in  very  thin, 
lustrous  needles,  melting  at  124°,  and  is  deposited  from  glacial 
acetic  acid  in  long,  broad  needles. 

P-JDinitroparaxylenc  (1:4:2:3)  is  more  readily  soluble  in 
alcohol,  and  crystallizes  on  gradual  evaporation  in  monoclinic 
tablets,  which  resemble  crystals  of  calcspar,  and  melt  at  93°.3 
It  is  a  characteristic  property  of  these  two  nitroxylenes  that 
equal  molecules  of  them  combine  to  form  a  double  compound, 
which  can  be  crystallized  from  glacial  acetic  acid,  but  is  de- 
composed by  alcohol  into  its  constituents.4  It  forms  transparent 
monoclinic  prisms  with  sphenoid  faces,  and  melts  at  99'5°. 

<y-Dinitroparaxylene  (1:4:2:5)  is  slightly  soluble  in  cold , 
more  readily  injiot  alcohol,  and  forms  long,  yellow  needles  with 
a  vitreous  lustre,  which  melt  at  147° — 1480.5 

Lellmann  determined  the  constitutions  of  these  three  isomerides 
by  the  methods  already  described  (Part  III.,  p.  245) ;  the  first 
two,  which  are  formed  in  largest  quantity,  were  converted  into 
the  hydrochlorides  of  the  corresponding  diamines,  their  solutions 
evaporated  with  ammonium  thiocyanate,'and  the  residues  heated 
to  120°,  ground  up  with  water,  washed,  dissolved  in  caustic  soda, 
and  these  solutions  heated  with  lead  acetate'.  The  a- compound 
gave  a  precipitate  of  lead  sulphide  while  the  /3-compound  did 
not,  and  was  thus  proved  to  be  an  orthodiamine. 

He  then  prepared  the  free  a-diamidoparaxylene,  which  is  a 
crystalline  mass,  and  combines  with  allyl  mustard  oil  to  form  the 
compound  C6H2(CH3)2(NH.CS.NH.C3H5)2,  which  crystallizes  in 

1  Luhmann,  Ann.  Chem.  Pharm.  cxliv.  276  ;  Fittig,  loc.  cit.  ;  Grevingk,  loc  cit. 

2  Jannasch,  Ann.  Chem.  Pharm.  clxxvi.  55  ;  Nblting  and  Forel,  loc.  cit. 

3  Fittig  and  Glinzer,   Ann.   Chem.  Pharm.  cxxxvi.  307 ;  Fittig,  Ahrens  and 
Mattheides,  ibid,  cxlvii.  17. 

4  Jannasch  and  Stiinkel,  Ber.  Deutsch.  Chem.   Ges.  xiv.  1146. 
6  Lellmann,  Ann.  Chem.  Pharm.  ccxxviii.  250. 


398  AROMATIC  COMPOUNDS. 

small  needles,  melting  without  decomposition  at  112'5°.  It  is 
therefore  a  metadiamine,  and  the  ^-compound  must,  accordingly, 
contain  the  nitroxyl  groups  in  the  para-position. 

Trinitroparaxylene,  C6H(CH3)2(NO2)3  (1:4:2:3: 5),  may 
readily  be  prepared  by  nitrating  with  a  mixture  of  nitric  and 
sulphuric  acids,  the  whole  being  gently  heated  at  the  close  of  the 
operation.  It  crystallizes  from  alcohol  in  stellate  aggregates  of 
dazzling  white  needles,  which  melt  at  139° — 1400.1 


XYLENESULPHONIC   ACIDS,  C6H3(CH3)2S03H. 

2212  Orthoxylenesulphonic  acid  (1:2:4)  is  formed  by  dis- 
solving orthoxylene  in  tolerably  hot  sulphuric  acid.  It  crystal- 
lizes from  a  somewhat  dilute  acid  solution  with  two  molecules 
of  water  in  long,  rectangular  tablets  or  thicker,  flat  prisms  with 
pointed  ends.  Its  salts  crystallize  extremely  well.  When  its 
potassium  salt  is  heated  with  sodium  formate,  paraxylic  acid  is 
formed. 

Sodium  orthoxylenesulphonate,  C6H2(CH3)2S03Na  +  5H2O, 
separates  from  a  concentrated  solution  in  flat  prisms,  the  size  of 
which  seems  only  to  be  limited  by  that  of  the  containing  vessel ; 
they  soon  effloresce  on  exposure  to  the  air. 

Orthoxylenesulphonic  chloride,  C6H3(CH3)2S02C1,  crystallizes 
from  ether  in  prisms,  melting  at  51° — 52°. 

Orthoxylenesulphonamide,  C6H3(CH3)2S02.NH2,  separates  from 
hot  alcohol  in  prisms,  which  melt  at  1440.2 

a-Metaxylenesulphonic  acid  (1:3:  4)  is  formed,  together  with 
a  small  quantity  of  the  isomeric  compound,  when  metaxylene  is 
dissolved  in  sulphuric  acid.  It  separates  on  the  addition  of  a 
little  water  in  large  plates  or  prisms,  which  contain  two  molecules 
of  water.  Xylic  acid  is  formed  when  potassium  salt  is  heated 
with  sodium  formate  (p.  391). 

Sodium  metaxylenesulphonate,  C6H3(CH3)2S03Na,  crystallizes 
from  water  in  scales,  and  from  alcohol  in  small  plates  possessing 
a  silver  lustre. 

a-Metaxylenesul phonic  chloride  solidifies  in  the  cold  to  a  radiating 
mass,  or  to  prisms  which  melt  at  34°. 

1  Fittig  and  Glinzer ;  Nolting  and  Geissmann,  Ber.  Dcutf.ch.  Chnn.  Oes.  xix. 
144.  2  Jacobsen,  -ib-ul.  x.  1010  ;  xi.  22. 


XYLENOLS.  399 


a-Metaxylenesulphamide  crystallizes  from  water  in  long 
pointed  needles  and  melts  at  137°. 

v-Metaxylenesulphonic  acid  (1:3:2)  has  not  been  prepared 
pure ;  its  calcium  salt  when  heated  with  sodium  formate  yields 
a  xylic  acid,  which  decomposes  on  distillation  with  lime 
into  carbon  dioxide  and  metaxylene.  Its  chloride  is  an  oily 
liquid,  and  the  amide  crystallizes  in  needles,  melting  at 
95°— 96.1 

ParaxylenesulpJionic  acid  is  formed  when  paraxylene  is  dis- 
solved at  a  gentle  heat  in  slightly  fuming  sulphuric  acid.  It 
crystallizes  with  two  molecules  of  water  in  large  plates  or  very 
long,  flat  prisms. 

Sodium  paraxylenesidphonate,  C6H3(CH3)2S03Na  +  H2O,  crys- 
tallizes in  large,  flat,  striated  prisms,  which  do  not  effloresce  in 
the  air. 

ParaxylenesulpJionic  chloride  forms  flat  prisms,  which  melt 
at  24°— 26° 

Paraxylenesnlphamide  is  readily  soluble  in  alcohol,  slightly 
in  boiling  water,  from  which  it  crystallizes  in  splendid,  long 
needles,  melting  at  147° — 148°  (Jacobsen). 


HYDROXY-XYLENES,  OR  XYLENOLS, 
C6H3(CH3)2OH. 

2213  After  Dusart,  Kekule  and  Wurtz  had  shown  that 
sulphonic  acids  are  converted  into  phenols  by  fusion  with  potash, 
the  last-named  of  these  chemists  applied  the  reaction  to  xylene, 
and  discovered  the  interesting  fact  that  this  hydrocarbon  yields 
two  isomeric  phenols,  a  solid  and  a  liquid  xylenol.  This  iso- 
merism  is  explained  by  him  as  due  to  the  different  positions  of 
the  hydroxyl  with  relation  to  the  two  methyl  groups.  "  This 
isomerism,"  he  adds,  "could,  according  to  Kekule's  beautiful 
theory,  also  exist  in  xylene  itself,  as  a  result  of  a  different 
arrangement  of  the  side  chains  in  the  nucleus."2  After  this 
supposition  had  been  proved  correct  and  these  xylenes  were 
known,  it  was  seen  that  six  xylenols  must  exist,  and  these  have 
all  now  been  prepared.  Jacobsen  obtained  four  of  them  from 

1  Jacobsen,  Ann.  Chem.  Pharm.  clxxxiv.  188  ;  loc.  cit. 

2  Ann.  Chem.  Pharm.  cxlvii.  372  ;  see  also  Wroblewsky,  Zeitschr.  Chem.  1868, 
232. 


400  AROMATIC  COMPOUNDS. 

the  sulphonic  acids  just  described,1  and  the  two  others  have  been 
prepared  from  the  xylidines  by  means  of  the  diazo-reaction.2 
Like  ordinary  phenol,  they  readily  form  tribromo-derivatives. 

The  xylenols  also  occur  in  coal-tar.  They  have  not,  in- 
deed been  isolated,  but  their  derivatives  have  been  prepared 
from  it. 

The  tar  obtained  as  a  by-product  from  blast  furnaces 
which  are  worked  with  coal  seems  to  be  especially  rich  in 
xylenols ;  the  creosote  oil  fraction,  boiling  at  210° — 240°,  when 
distilled  over  heated  zinc  dust,  yielded  a  mixture  of  hydrocarbons, 
which  consisted  chiefly  of  metaxylene.3 

a-OrtJwxylcnol  (1:2:4)  crystallizes  from  hot  water  in  very 
long  needles  and  from  very  dilute  alcohol  in  rhombic  pyramids, 
melting  at  62*5° ; 4  it  boils  at  225°  and  forms  an  aqueous  solution 
which  is  not  coloured  by  ferric  chloride. 

a-Tribromorthoxylenol,  C6Br3(CH3)2OH,  crystallizes  from 
alcohol  in  fine,  snow-white,  matted  needles,  melting  at  169°. 

v-Orthoxylenol  (1:2: 3)  crystallizes  from  water  in  white 
needles,  melts  at  75°  and  boils  at  218°;  its  aqueous  solution 
is  coloured  blue  by  ferric  chloride,  but  is  not  affected  by 
bleaching-powder  solution. 

a-Metaxylenol  (1:3:4)  is,  according  to  Jacobsen,  a  strongly 
refractive  liquid,  which  smells  like  phenol,  boils  at  211 '5°  and 
becomes  viscid  at  —20°,  without,  however,  solidifying.  These  are 
also  the  properties  of  the  liquid  xylenol  discovered  by  Wurtz, 
while  Stadel  and  Holz  showed  that  the  xylenol  prepared  from 
pure  a-metaxylidine  solidifies  at  the  ordinary  temperature.5 
Jacobsen,  on  reinvestigation,  found  that  his  preparation  crystal- 
lized after  repeated  cooling  or  on  the  addition  of  a  small  crystal.6 
It  forms  white  needles,  melting  at  26°.  It  dissolves  slightly 
in  water,  yielding  a  solution  which  is  coloured  blue  by  ferric 
chloride ;  the  alcoholic  solution,  on  the  other  hand,  is  coloured 
a  splendid  dark  green,  which  passes  into  blue  when  water  is 
added. 

a-Metaxylenyl  methyl  ether,  C6H3(CH3)2OCH3,  is  a  liquid 
which  has  a  faint  smell  resembling  that  of  benzene,  and  boils 
at  192°. 


1  Bcr.  Deutsch.  Chem.  Gcs.  xi.  23. 

2  Thol,  ibid,  xviii.  359,  2561  ;  Nolting  and  Forel,  ibid,  xviii.  2668. 

3  Smith,  Coutts  and  Brothers,  Journ.  Chem.  Soc.  1886,  i.  17. 

4  Jacobsen,  Ber.  Deutsch.  Chem.  Ges.  xvii.  161. 
8  Ber.  Deutsch.  Chem.  Ges.  xviii.  2921. 

6  Ibid,  xviii.  3463. 


PARAXYLENOL.  401 


a-Metaxylenyl  acetate,  C6H3(CH3)2O.CO.CH3,  is  a  liquid 
boiling  at  226°,  which  has  a  faint  odour  of  oil  of  bergamot. 

Melting-point. 

a-Bromometaxylenol,  C8H8Br.OH,  oily  liquid  .     .     . 
a-Dibromometaxylenol,  C8H7Br2.OH,  fine,  colourless  )    ,-„<> 

needles j 

a-Tribromometaxylenol,  C8H6Br3.OH,  long,  colourless  ) 

needles j 

v-Metaxyknol  (1:3:2)  crystallizes  in  silky  plates  or  long, 
flat  needles,  melts  at  74'5°,  boils  at  211°— 212°,  and  gives  no 
colouration  with  ferric  chloride. 

v-  Tribromometaxylenol  crystallizes  from  hot  alcohol  in  long, 
light  yellow  needles,  melting  at  175°. 

s-Metaxylenol  (1:3:5)  is  deposited  from  solution  in  hot 
water  or  from  sublimation  in  splendid  white  needles,  melting 
at  68°.  It  boils  at  219'5°,  and  gives  no  colouration  with  ferric 
chloride. 

s- Tribromometaxylenol  crystallizes  from  alcohol  or  benzene  in 
fine,  white  needles,  melting  at  166°. 

Paraxylenol  (1  :  4  :  2)  has  been  prepared  from  paraxylidine  ; 1 
it  melts  at  74' 5°,  sublimes  in  needles  at  a  slightly  higher 
temperature,  boils  at  21 1*5°  and  crystallizes  from  hot  water  or 
very  dilute  alcohol  in  large,  flat  needles.  It  gives  no  colouration 
with  ferric  chloride.  The  solid  compound  prepared  by  Wurtz 
was  almost  pure  paraxylenol. 

Melting-point. 

Monobromoparaxylenol,  CLILBr.OH,  colourless,  flex-  (    Qh7o 
ible  needles f   87 

Tribromoparaxylenol,    C8H6Br3.OH,    deep     golden  \  ..  ,_-<> 
yellow  needles J 

The  great  similarity  existing  between  para-  and  v-meta- 
xylenol  is  somewhat  remarkable  (Jacobsen). 

A  xylenol  occurs  in  crude  creosote,  which  boils  at  220°,  does 
not  crystallize,  and  on  heating  with  potash  and  methyl  iodide 
yields  a  methyl  ether,  boiling  at  2000.2  This  substance  is  pro- 
bably a  mixture,  and,  from  its  high  boiling-point,  would  seem  to 
consist  chiefly  of  a-orthoxylenol.s 

1  Nolting,  Witt  and  Forel,  Bor.  Deittach.  Chem.  Ges.  xviii.  2664. 

2  Marasse,    Ann.    Chem.    Pharm.   clii.   75  ;  Tiemann  and   Mendelsohn,  Ber. 
D&utseh.  Chem.  Gcs.  x.  57. 

8  N  citing,  Witt  and  Forel,  ibid,  xviii.  2664. 


402  AROMATIC  COMPOUNDS. 

Robiquet,  by  the  distillation  of  aloes  with  lime,  obtained  a 
liquid  which  he  called  alo'isol.  This  substance  has  been  shown 
by  Rembold  to  be  a  mixture,  the  portion  soluble  in  alkalis  having 
the  composition  of  a  xylenol.1 


DIHYDROXY-XYLENES,  C6H2(CH3)2(OH)2. 

2214  Homorcinol,  or  Paraxylorcinol  (1:4:2:6),  was  obtained 
by  Stenhouse  from  Usnea  larbata  and  Cladonia  rangiferina, 
and  named  by  him  /3-orcin,2  a  name  which  was  subsequently 
changed  by  him  and  Groves  into  beta-orcinol.  It  is  a  decom- 
position product  of  the  barbatic  acid,  C19H20O7,  which  occurs  in 
these  lichens.3  Lamparter  has  succeeded  in  obtaining  it,  together 
with  orcinol,  from  Eocella  fuciformis* 

Its  constitution  was  determined  by  Kostanecki,  who  prepared 
it  from  a-nitroparaxylidine,  by  first  converting  it  into  nitroxylenol, 
reducing  this  to  amidoxylenol,  and  finally  passing  from  this  to 
paraxylorcinol  by  means  of  the  diazo-reaction.5 

It  is  less  soluble  in  water  than  orcinol,  and  is  deposited  in 
quadratic  crystals,  melting  at  163°.  It  possesses  a  slightly  sweet 
taste,  boils  at  277° — 280°,  and  is  coloured  red  by  ammonia  in 
presence  of  air  more  rapidly  than  orcinol.  Its  aqueous  solution 
gives  with  ferric  chloride  a  light  carmine-red  colouration,  quite 
distinct  from  the  purple-red  produced  with  orcinol.  Like  the 
latter  it  yields  a  red  solution  with  a  beautiful  green  fluorescence 
when  heated  with  chloroform  and  caustic  soda  (Kostanecki). 

Nitrosoparaxylortinol,  C6H(CH3)2(OH)0(NOH),  is  formed  by 
the  action  of  nitrosyl  sulphate  (Part  III.  p.  171)  on  an  aqueous 
solution  of  paraxylorcinol,  as  a  lustrous,  orange-red  precipitate, 
which  crystallizes  from  glacial  acetic  acid  in  small,  lustrous,  red 
prisms. 

Metaxyloroinol  (1:3:4:6)  is  obtained  from  s-nitro-a-meta- 
xylidine.  It  is  readily  soluble  in  water,  has  an  acid  taste,  melts 
at  125°  and  boils  at  276°— 279°.  It  crystallizes  from  chloroform 
in  brilliant  white,  monosymmetric  plates,  which  can  also  be 
obtained  by  sublimation.  No  red  colouration  is  produced  by 
exposure  to  ammonia  and  air.6 

1  Ann.  Chcm.  PJiarm.  cxxxviii.  186.  2  Phil.  Traits.  1848,  63. 

3  Ibid,  cciii.  285.  •*  Ibid,  cxxxiv.  243. 

5  Bcr.  Deutsch.  Chem.  Gfcs.  xix.  2318. 
tf  Pfaff,  ibid.  xvi.  611  and  1135  ;  Kostanecki,  loc.  cit. 


TRIHYDROXY-XYLENES.  403 

Gundelach,  by  heating  chlorometaxylenesulphoiiic  acid  to 
230° — 250°  with  caustic  potash,  obtained  a  dihydroxy-xylene 
which  should  be  identical  with  metaxylorcinol,  since,  according 
to  Jacobsen,  the  side  chains  of  the  sulphonic  acid  have  the 
following  arrangement :  CH3  :  CH3  :  Cl :  SO3H  =  1  :  3  : 4  :  6.1  It 
crystallizes  in  microscopic  prisms,  which  are  tolerably  soluble  in 
water,  melt  at  120°  and  are  coloured  deep  red  by  ammoniacal 
air.2  This  compound  is  probably  impure  metaxylorcinol. 

The  following  dihydroxy-xylenes  have  been  prepared  by  the 
reduction  of  the  xyloquinones : 

Paraxyloquinol,  QT  Hydrophlorone  (1  : 4  :  2  :  5),  is  readily  soluble 
in  alcohol,  slightly  in  boiling  water  and  benzene,  and  crystallizes 
in  nacreous  plates  or  tablets,  which  melt  at  210°  and  sublime  in 
long  needles.  It  reduces  silver  solution  and  is  re-oxidized  to  the 
quinone  by  ferric  chloride.  The  diethyl  ether,  C8H8(OC2H5)2,  is 
formed  by  heating  it  with  ethyl  bromide  and  caustic  potash ;  it 
forms  lustrous  plates,  which  melt  at  105° — 106°,  and  have  an 
odour  resembling  that  of  peppermint  (Stiidel  and  Holz). 

Metaxyloyuinol  (1:3:2:5)  sublimes  in  needles  and  melts  at 
149°. 

Ortlwxyloquinol  (1:2:3:6)  crystallizes  from  water  in  crusts, 
which  melt  at  221°  with  decomposition. 


TRIHYDROXY-XYLENES. 

2215  Trihydroxymetaxylene,C^(fll^^z(Q'S)^i^  formed  by  the 
reduction  of  hydroxymetaxyloquinone  (p.  404)  with  sulphurous 
acid.  It  is  tolerably  soluble  in  cold,  readily  in  hot  water,  and 
crystallizes  in  colourless  or  yellowish  transparent  tablets,  con- 
taining a  molecule  of  water,  which  is  lost  at  80°,  the  anhydrous 
compound  melting  at  121° — 122°.  It  is  reduced  to  metaxylene 
when  heated  with  zinc-dust.  Oxidizing  agents  readily  convert 
it  into  the  quinone  ;  if  the  aqueous  solution  be  merely  allowed 
to  evaporate  in  the  air,  the  quinhydrone  crystallizes  out  in  long 
needles  resembling  those  of  potassium  permanganate. 

Triacetoxy metaxylene,  C6H(CH3)2(O.CO.CH3)3,  is  obtained  by 
the  action  of  acetyl  chloride,  and  crystallizes  from  alcohol  in 
colourless,  lustrous  prisms,  which  melt  at  99°,  and  sublime 
without  decomposition  when  carefully  heated. 

1  Ber.  Deutsch.  Chcm.  Gcs.  xviii.  1762.  2  Bull.  Soc.  Chim.  xxviii.  343. 


404  AROMATIC  COMPOUNDS. 


THE  XYLOQUINONES,  C6H2(CH3)2O2. 

2216  Paraxyloquinone  (1:4:2:5).  Rommier  and  Bouilhon, 
by  oxidizing  the  fraction  of  crude  cresol  boiling  between  195°- 
220°  with  sulphuric  acid  and  manganese  dioxide,  obtained  two 
isomeric  quinones,  C8H802,  and  gave  to  the  one,  which  is  formed 
in  larger  quantity  and  melts  at  60° — 62°,  the  name  of  phlorone, 
and  to  the  other,  melting  at  125°,  that  of  metaphlorone.1  Accord- 
ing to  Gorup-Besanez  and  v.  Rad,  phlorone  is  also  formed  by  the 
oxidation  of  wood-tar  creosote.2  Nietzki  then  obtained  para- 
xyloquinone  by  the  oxidation  of  crude  xylidine  and  of  paradi- 
amidoxylene  with  potassium  dichromate  and  sulphuric  acid,  and 
found  that  its  properties  agree  with  those  of  metaphlorone  ; 3 
Carstanjen  then  showed  that  phlorone  is  a  mixture  of  toluquinone 
with  paraxyloquinone,  and  that  the  latter  yields  paraxylene  on 
heating  with  zinc-dust.4  It  is  best  prepared  from  paraxylidine 
in  the  same  way  as  benzoquinone  from  aniline.5 

Paraxyloquinone  is  only  slightly  soluble  in  water  and  cold 
alcohol ;  it  crystallizes  from  hot  alcohol  in  splendid  golden- 
yellow  needles,  which  melt  at  123'5°  and  readily  sublime. 

Ortboxyloquinone  (1:2:3:6)  has  been  prepared  from  v-ortho- 
xylidine  by  oxidation ;  it  is  slightly  soluble  in  water,  more 
readily  in  alcohol,  and  sublimes  in  yellow  needles,  which  melt 
at  55°. 

Metaxyloquinone  (1:3:2:5)  is  formed  by  the  oxidation  of 
v-  and  s-metaxylidine,  and  crystallizes  in  splendid  yellow  needles, 
melting  at  73°. 

Hydroxymetaxyloquinone,  C6H(CH3)2(OH)02,  is  formed  when 
diamidomesitylene,  C6H(CH3)3(NH2)2,  is  distilled  with  potassium 
dichromate  and  dilute  sulphuric  acid.  It  crystallizes  from  hot 
water  or  ether  in  orange-red  needles,  has  a  characteristic  smell 
resembling  that  of  benzoquinone,  melts  at  103°,  and  sublimes 
very  readily  in  splendid,  lustrous,  deep  golden-yellow  needles. 
Its  aqueous  solution  is  instantly  coloured  a  splendid  reddish 
violet  by  the  addition  of  any  alkaline  substance,  and'  this 
reaction  is  so  delicate  that  the  slightest  traces  of  the  quinone 

1  Compt,  Rend.  Iv.  214. 

2  Zeitschr.  Chem.  [2]  iv.  560  ;  Ann.   Chem.  Pharm.  cli.  158. 

3  Bcr.  Deutsch.  Chem.  Gcs.  xiii.  470. 

4  Journ.  Prakt.  Chem.  [2]  xxiii.  421. 

6  bolting  and  Forel,  Ber.  Deutsdi.  Chem.  Gcs.  xviii.  2668. 


AMIDOXYLENES.  405 


can  be  detected  by  it.  Insoluble  carbonates  also  produce  this 
colouration ;  thus,  if  a  O'l  per  cent,  solution  of  the  quinone  be 
shaken  up  with  calcium  carbonate,  the  colouration  produced  is 
so  deep  that  even  a  thin  layer  of  the  liquid  appears  quite 
opaque.  The  presence  of  calcium  carbonate  can  thus  be  shown 
in  very  small  quantities  of  mineral  waters  ;  free  carbonic  acid 
does  not  affect  the  colouration,  so  that  the  quinone  forms  a 
valuable  indicator  for  alkalimetry. 

It  forms  salts,  which  readily  decompose  on  warming  or  on 
exposure  to  the  air  in  presence  of  an  excess  of  the  base.  The 
potassium  salt,  C8H7(OK)O2,  crystallizes  from  hot  alcohol  in 
small,  black  needles,  1  mgrm.  of  which  is  sufficient  to  impart  a 
deep  red  colour  to  a  litre  of  water.1 


AMIDO-DERIVATIVES  OF  THE  XYLENES. 

THE  AMIDOXYLENES,  OR  XYLIDINES,  C6H3(CH3)2NH2. 

2217  Cahours  gave  the  name  of  xylidine  to  the  homologue  of 
toluidine  and  aniline  which  he  obtained  from  his  xylene  (p.  386), 
>y  nitrating  it  and  submitting  the  nitroxylene  formed  to  reduc- 
tion. This  substance  and  the  xylidine  obtained  by  Church  in 
the  same  manner  was  obviously  a  mixture  of  toluidines  and 
xylidines,  while  that  prepared  by  Deumelandt  from  xylene 
boiling  at  140°  consisted  chiefly  of  a-metaxylidine,  as  was  also 
the  case  with  that  prepared  by  Hofmann  and  Martius  by  heating 
paratoluidine  hydrochloride  to  300°  with  methyl  alcohol.  It 
only  became  possible  to  obtain  the  six  xylidines  after  the  three 
xylenes  had  been  obtained  in  the  pure  condition  and  the  six 
nitroxylenes  prepared  from  these.  A  mixture  of  them  is  manu- 
factured on  the  large  scale  from  tar-xylene,  and  the  purity  and 
composition  of  commercial  xylidine  is  therefore  dependent  on 
that  of  the  latter.  Specimens  now  come  into  the  market 
containing  as  much  as  25  per  cent,  of  paraxylidine  in  addition 
to  ordinary  metaxylidine.2 

The  commercial  product  is  employed  in  the  manufacture  of 
azo-colours  and  of  the  cumidines,  C6H2(CH3)3NH2,  which  are 
obtained  by  heating  the  hydrochlorides  with  wood-spirit. 

1  Fittig  and  Siepermann,  Ann.  Chem.  Pharm.  clxxx.  27. 

2  Nblting,  Witt  and  Forel,  Ber.  Deutsch.   Chem,  Ges.  xviii.  2664  ;  Stadel  and 
Holz,  ibid,  xviii.  2919. 

257 


406  AROMATIC  COMPOUNDS. 

v-Ortlioxylidine  (1:2:3)  is  formed  when  solid  dibromortho- 
xylene  is  nitrated,  the  nitrodibromorthoxylene  reduced  to  dibromo- 
xylidine,  and  the  bromine  removed  by  treatment  with  sodium 
amalgam  and  water.1  It  is  a  liquid  which  boils  at  223°;  its 
hydrochloride  is  tolerably  soluble  in  water,  and  crystallizes  in 
white  needles,  containing  a  molecule  of  water.  The  sulphate  is 
only  slightly  soluble. 

v-Acetorthoxylide,  C6H3(CH3)2NH(CO.CH3),  crystallizes  from 
hot  benzene  in  white  needles,  melting  at  1340.3 

a-Orthoxylidine  (1:2:4)  melts  at  49°  and  boils  at  226°.  It 
is  tolerably  soluble  in  hot  water,  readily  in  alcohol,  and  crystal- 
lizes when  caused  to  solidify  quickly  or  when  rapidly  deposited 
from  solution,  in  transparent,  vitreous  tablets,  while  it  may  be 
obtained  by  the  gradual  evaporation  of  its  petroleum-ether 
solution  in  thick,  monoclinic  crystals.  Its  aqueous  solution  is 
not  coloured  by  bleaching  powder;  the  solutions  of  its  salts 
colour  pine-wood  an  intense  yellow. 

The  hydrochloride  is  readily  soluble  in  water,  but  only 
slightly  in  hydrochloric  acid,  and  crystallizes  with  one  molecule 
of  water  in  long,  very  thin  prisms. 

a-Acetorthoxylide  crystallizes  from  hot  water  containing  a  little 
alcohol  in  long,  thin,  vitreous  prisms,  which  melt  at  99°. 

The  base  is  converted  by  the  diazo-reaction  into  a-ortho- 
xylenol.3 

v-Metaxylidine  (1:3:2)  was  first  obtained  by  Schmitz  by 
heating  /3-amidomesitylenic  acid,  C6H2(CH3)2(NH2)CO2H,  with 
lime.4  Grevingk,5  and  Nolting  and  Forel,6  then  prepared  it  from 
v-nitrometaxylene.  It  is  a  liquid  boiling  at  214°. 

Its  hydrochloride  crystallizes  in  thin,  anhydrous,  monoclinic 
plates,  which  are  readily  soluble  in  water. 

v-Acetmetaxylide  crystallizes  from  benzene  in  white  needles, 
which  melt  at  176  8°.  It  is  not  attacked  by  caustic  potash 
solution,  sulphuric  acid,  or  hydrochloric  acid,  on  heating  in  an 
open  vessel,  but  is  decomposed  by  the  last  of  these  at  150°. 

a-Metaxylidine  (1:3:4)  has  been  known  for  a  longer  period 
than  any  of  its  isomerides  and  is  therefore  also  called  ordinary 
metaxylidine.  It  is  formed  by  the  distillation  of  a-amidomesity- 
lenic  acid  with  lime  (Schmitz)  and  by  the  reduction  of  a-nitro- 

1  Thol,  Ber.  Deutsch.  Chem.  Gas.  xviii.  2561  ;  Wroblewsky,  ibid,  xviii.  2904, 
xix.  235  ;  Jacobsen,  ibid,  xviii.  3166. 

2  Nolting  and  Forel,  ibid,  xviii.  2668.      8  Jacobsen,  ibid.  xvii.  159. 

4  Ann.  Chem.  Pharm.  cxciii.  377.  6  Ber.  Deutsch.  Chem.  Ges.  xvii.  2422. 

6  Ibid  xviii.  2676. 


XYLIDINES.  407 


• 


metaxylene.1  It  may  also  be  readily  obtained  from  commercial 
xylidine  by  converting  this  into  the  hydrochloride  and  purifying 
by  re-crystallization.  In  order  to  obtain  it  perfectly  pure,  the  acet- 
xylide  is  prepared,  purified  by  re-crystallization,  and  decomposed 
with  sulphuric  acid.  The  other  xylidine  can  also  be-  easily 
obtained  pure  in  this  way.  It  is  a  liquid  boiling  at  212°. 

The  hydrochloride  is  only  slightly  soluble  in  cold  water,  and 
crystallizes  in  anhydrous,  rhombic  tablets;  the  hydrobromide 
crystallizes  even  better,  forming  splendid  prisms  (Stadel  andHolz). 

a-Acetmetaxylide  crystallizes  from  benzene  in  white  needles 
melting  at  129° ;  impurities  cause  a  considerable  lowering  of  the 
melting-point. 

s-Mttaxylidine  (1:3:5)  is  obtained  by  the  reduction  of  the 
corresponding  nitroxylene  ; 2  it  is  a  liquid  boiling  at  220°.  Its 
hydrochloride  and  nitrate  crystallize  in  large,  anhydrous  needles ; 
4 '66  parts  of  the  latter  dissolve  in  100  parts  of  water  at  13°. 

s-Acetmetaxylide  crystallizes  from  alcohol  in  large,  flat  needles, 
melting  at  140'5°. 

Paraxylidine  (1:4:2)  may  be  prepared  in  the  usual  way  by  the 
reduction  of  nitroparaxylene,3  and  also  from  commercial  xylidine ; 
the  latter  is  run  into  fuming  sulphuric  acid  containing  sufficient 
trioxide  to  convert  the  bases  into  sulphonic  acids,  the  mixture 
being  well  stirred  and  then  heated  on  the  water-bath.  The 
solution  is  allowed  to  cool  and  the  solid  mass  pressed  under  water 
to  separate  the  metaxylidinesulphonic  acid  in  the  crystalline 
state.  The  sodium  salt  of  paraxylidinesulphonic  acid  is  then 
prepared  from  the  mother-liquor  by  neutralizing  it  with  lime, 
filtering,  removing  the  calcium  with  carbonate  of  soda,  and 
concentrating  the  filtrate.  It  separates  in  splendid,  nacreous 
plates,  which  are  freed  from  any  adhering  traces  of  the  readily 
soluble  salt  of  the  metaxylidinesulphonic  acid  by  washing  with 
a  little  cold  water.  P.ure  paraxylidine  is  then  obtained  by  the 
dry  distillation  of  the  salt.4 

It  is  a  liquid  boiling  at  215°;  its  hydrochloride  and  nitrate 
crystallize  in  flat  needles  or  large  tablets,  and  the  sulphate,  which 
is  only  slightly  soluble,  forms  small  plates. 

Acetparaxylide  crystallizes  from  hot  water  or  toluene  in  long 
lustrous  needles,  melting  at  139°. 

1  Tawildarow,  Zeitschr.  Chem.  1870,  418  ;  Nolting  and  Forel,  loc.  cit. 

2  Wroblewsky,  Ann.  Chem.  Pharm.  ccvii.  95  ;  Thol,  Ber.  Deutsch.  Chem.  Ges. 
xviii.  359  ;  Nolting  and  Forel,  loc.  cit. 

3  Schaumann,  Ber.  Deutsch.  Chcm.  Ges.  xi.   1537  ;  Nolting  and  Forel.  ibid. 
viii.  2680.  4  Nolting,  Witt  and  Forel,  xviii.  2664. 


408  AROMATIC  COMPOUNDS. 


NITROXYLIDINES,  C6H2(CH3)2(NH2)2N02. 

2218  $-Nitro-a-metaxylidine  (1:3:4:6)  is  formed  by  the 
reduction  of  s-dinitrometaxylene  with  ammonium  sulphide,  and 
crystallizes  from  hot  water  or  alcohol  in  orange-red  needles, 
while  it  separates  on  the  gradual  evaporation  of  its  alcoholic 
solution  in  thick,  deep  red  crystals,  which  melt  at  1230.1 

v-Nitro-a-metaxylidine  (1:3:4:2)  has  also  been  prepared  from 
v-dinitrometaxylene,  and  forms  golden-yellow  needles,  which 
melt  at  78°.2 

a-Nitro-a-metaxylidine  (1:3:4:5).  In  order  to  prepare  this 
compound,  a-acetmetaxylide  is  treated  with  concentrated  nitric 
acid  in  the  cold,  and  the  product  decomposed  by  heating  with 
sulphuric  acid,  diluted  with  half  its  volume  of  water.  It 
crystallizes  from  alcohol  in  long,  red  needles,  which  melt  at  76°.3 

A  small  quantity  of  s-nitro-a-metaxylidine  is  formed  at  the 
same  time  (Nblting  and  Forel); 

a-Nitro-s-metaxylidine  (1  : 3  :  5  :  4)  is  obtained  by  the  nitration 
of  s-metaxylidine  with  a  mixture  of  nitric  and  sulphuric  acids ; 
it  crystallizes  in  yellow  needles,  which  melt  at  54°,  and  readily 
volatilize  with  steam  (Nolting  and  Forel). 

a-Nitroparaxylidine  (1:4:2:6)  has  been  prepared  by  the 
reduction  of  a-dinitroparaxylene  with  ammonium  sulphide,  and 
crystallizes  from  alcohol  in  long,  golden-yellow  needles,  melting 
at  96°.4 

fS-Nitroparaxylidine  has  not  yet  been  obtained,  as  the  cor- 
responding dinitroparaxylene  is  immediately  reduced  to  the 
diamine  by  ammonium  sulphide. 

y-Nilroparaxylidine  (1:4:2:5)  is  formed  by  the  nitration  of 
paraxylidine  with  a  mixture  of  sulphuric  and  nitric  acids,  and 
forms  brownish  yellow,  lustrous  crystals,  which  are  readily  soluble 
in  alcohol  and  melt  at  1420.5 

Dinitroparaxylidine,  C6H(CH3)2(N02)2NH2  (5:2:  3),  is  ob- 
tained by  the  long-continued  heating  of  trinitroparaxylene  with 

1  Fittig,  Ahrens  and  Mattheides,  Ann.  Chcm.  Pharm.  cxlvii.  18. 

2  Grevingk,  Ber.  DeuLsch.  Chcm.  Ges.  xvii.  2425. 

3  Hofmann,  ibid.  ix.  1295  ;  Wroblewsky,  Ann.  Chem.  Phwrn.  ccvii.  91  ;  Thbl, 
Ber.  Dcutsch.  Chcm.  Ges.  xviii.  359  ;  Nolting  and  Forel,  ibid,  xviii.  2677. 

4  Fittig,  Ahrens  and  Mattheides,  Ann.  Chcm.  Pharm.  cxlvii.  22. 

5  Nolting,  Witt  and  Forel,  Ber.  Deutsch.  Chcm.  Ges.  xviii.  2664. 


DIAMIDO  XYLENES.  409 


alcoholic  ammonia.  It  crystallizes  from  glacial  acetic  acid  in 
yellow  needles,  which  melt  at  202° — 203°,  and  are  converted  by 
the  diazo-reaction  into  a-dinitroparaxylene.1 


DIAMINES  AND  TRIAMINES  OF  THE 
XYLENES,  C 


2219  a-Diamidometaxylene,  C6Ha(CH3)2  (NH2)2  (1  :  3  :  4  :  5),  is 
formed  by  the  reduction  of  a-nitro-a-metaxylidine,2  and  amido- 
azo-a-metaxylene.3  It  crystallizes  from  hot  benzene  in  small, 
white  plates,  which  melt  at  77°  —  78°,  and  are  readily  soluble  in 
alcohol. 

s-Diamidometaxylene  (1:3:4:6)  has  been  prepared  from 
s-dinitrometaxylene  and  the  corresponding  nitroxylidene  ;  it 
sublimes  in  white  crystals,  melting  at  104°. 

v-Diamidometaxylene  (1  :  3  :  4  :  2)  sublimes  in  white  needles 
and  melts  at  64°. 

Nitrodiamidometaxylene,  C6H(CH3)2(NH2)2N02,  is  formed  by 
the  reduction  of  trinitrometaxylene  with  ammonium  sulphide 
and  was  first  described  by  Bussenius  and  Eisenstuck  as  nitro- 
petroldiamine  (p.  387).  It  is  slightly  soluble  in  cold,  more 
readily  in  boiling  water  and  readily  in  alcohol,  from  which 
it  crystallizes  in  lustrous,  ruby-red  prisms,  an  inch  in  length, 
which  melt  at  212°—  213°.  4 

Triamidometaxylene,  C6H(CH3)2(NH2)3  (1:3:2:4:6),  has 
been  obtained  by  reducing  trinitrometaxylene  with  hydrochloric 
acid  and  stannous  chloride  ;  it  crystallizes  in  white  needles,  which 
decompose  at  about  140°  without  melting. 

Diamidometaxylene  contains  the  amido-groups  in  the  ortho- 
position,  and  gives  all  the  characteristic  reactions  of  the  ortho- 
diamines  (Nolting  and  Forel)  ;  the  two  other  diamidometa- 
xylenes  are  metadiamines,  and  therefore  yield  azo-dyes  when  their 
hydrochlorides  are  treated  with  sodium  nitrite,  as  does  also 
triamidometaxylene.  The  colour  prepared  from  v-diamido- 
metaxylene  dyes  silk  reddish  brown,  that  from  s-diamidometa- 
xylene,  yellowish  brown,  while  the  derivative  of  the  triamine 

1  Nolting  and  Geissmann,  Ber.  Deutsch.  Cfwm.  Ges.  xix.  144. 

2  Hofmann,  ibid.  ix.  1298. 

3  Nolting  and  Forel,  ibid,  xviii.  2683. 

4  Fittig  and  Velguth,  Ann.  Chcm.  Pharm.  cxlviii.  6. 


410  AROMATIC  COMPOUNDS. 

produces  a  grey  shade  of  olive.  With  diazobenzenesulphonic 
acid,  on  the  other  hand,  the  v-diamine  gives  a  light  yellowish  red 
colouring  matter,  while  that  from  the  s-diamine  is  darker  and 
that  from  the  triamine  a  dark,  red-black.  The  shades  produced 
on  silk,  however,  are  in  the  inverse  relation ;  the  lightest  coloured 
dye  gives  the  darkest  shade,  then  follows  that  of  the  s-diamine, 
while  the  substance  prepared  from  the  triamine  dyes  an  almost 
pure  golden  yellow.1 

a-Diamidoparaxylene,  CflH2(CH8)2(NH2)2  (1:4:2:6),  sublimes 
in  white  needles,  melting  at  101*5° — 102'5°;  its  hydrochloride 
gives  a  brown  colouring  matter  with  sodium  nitrite;  it  forms 
chrysoidines  with  diazo-salts  and  a  dye  analogous  to  toluylene- 
blue  (p.  82)  with  nitrosodimethylaniline. 

fB-Diamidoparaxylene  (1:4:2:3)  sublimes  in  small  needles, 
melting  at  75°;  sodium  nitrite,  added  to  the  solution  of  its 
hydrochloride,  precipitates  an  azimido-compound  (Part  III. 
p.  270), 2  while  ferric  chloride  produces  a  deep  red  colouration. 

ry-Diamidoparaxylene  (1:4:2:  5).  Nietzki  prepared  this  com- 
pound by  the  action  of  zinc  and  hydrochloric  acid  on  the  amido- 
azoxylene,  C6H3(CH3)2.N2.C6H2(CH3)2NH2,  prepared  from  com- 
mercial xylidine.3  Nolting  and  Forel  then  obtained  it  from 
amido-azoparaxylene,  and  showed  that  Nietzki's  compound 
consists  of  amido-azometaparaxylene.4  It  is  also  formed  by  the 
reduction  of  7-nitroparaxylidine.  It  is  slightly  soluble  in  cold, 
readily  in  hot  water  and  alcohol,  but  less  readily  in  benzene, 
from  which  it  crystallizes  in  white  needles,  melting  at  146'5° — 
147°.  It  yields  paraxyloquinone  on  oxidation. 


XYLYL   COMPOUNDS. 

2220  When  an  atom  of  hydrogen  in  the  methyl  group  of  one 
of  the  xylenes  is  replaced  by  another  element  or  radical,  com- 
pounds of  the  monovalent  radical  xylyl,  CH3.C6H4.CH2,  are  ob- 
tained;  this  radical  has  also  been  called  tolyl,  because  the 
monobasic  acids,  CH3.C6H4.C02H,  which  correspond  to  the 
xylyl  alcohols,  CH3.C6H4.CH2.OH,  and  which  decompose  into 
toluene  and  carbon  dioxide  when  heated  with  lime,  have  received 

1  Grevingk,  Ber.  Deutsch.  Ckem.  Ges.  xvii.  2442. 

2  Nolting  and  Geissmann,  ibid.  xix.  144. 

3  Ibid.  xiii.  470.  4  Ibid,  xviii.  2685. 


XYLYL  COMPOUNDS.  411 

the  name  of  toluic  acids.     The  term  tolyl  has,  however,  been 
also  applied  to  the  group  C7H7,  and  it  is  therefore  preferable  to 
designate  the  derivatives  of  the  xylenes  as  xylyl  compounds.1 
The  use  of  this  term  is  open  to  the  objection  that  the  acids, 

|(CH3)2C6H3.CO2H,  are  called  xyiic  acids,  because  they  stand  to 
xylene  in  the  same  relation  as  the  toluic  acids  to  toluene  and 
benzoic  acid  to  benzene.2 
In  order  to  avoid  this  confusion  of  terms,  it  has  been  proposed 
to  give  the  name  of  tolyl  to  the  group  CH3.C6H4  and  to  desig- 
nate the  xylyl  alcohols  according  to  Kolbe's  nomenclature  as 
tolyl  carbinols,3  the  toluic  acids  being  called  tolylformic  acids. 
In  the  sequel,  however,  the  names  which  are  in  general  use  will 
be  retained. 

Chlorine  acts  upon  boiling  xylene  in  the  same  way  as  on 
toluene,  substitution  taking  place  in  the  methyl  group.  The 
first  xylyl-compounds  were  obtained  from  tar-xylene,  but  they 
have  now  been  prepared  from  the  pure  hydrocarbons.4 

Bromine  acts  on  the  xylenes  at  the  boiling-point  in  a  similar 
manner ; 5  an  energetic  reaction  also  takes  places  in  the  sunlight, 
the  first  product  consisting  of  a  mixture  of  xylyl  bromides.6 


XYLYL  ALCOHOLS,  CH3.C6H4.CH2.OH. 

Orihoxylyl  alcohol  was  prepared  by  Raymann  by  the  action  of 

sodium  amalgam  and   water   on   orthotolualdehyde,  which   he 

had  prepared  from  the  chloride.     It  is  slightly  soluble  in  water, 

iadily  in  alcohol,  and  crystallizes  in  needles,  melting  at  54°. 

Lccording  to  Colson,  who  prepared  it  by  heating  the  bromide 

with  water,  it  melts  at  34'2°  and  boils  at  2170.7 

Metaxylyl  alcohol  has  been  obtained  both  from  the  acetate 
and  bromide  ;  it  is  a  liquid,  which  boils  at  215°  and  has  a  faint 
odour. 

Metaxylyl  ethyl  ether,  CH3.C6H4.CH2.O.C2H6,  is  a  liquid  and 
boils  at  202°. 

1  Jahresb.  Chem.  1866,  605. 

2  Kekule,  Ann.  Chem.  Pharm.  cxxxvii.  186. 
1  Beilstein,  Org.  Chem.  1084. 

Raymann,  Bull.  Soc.  Chim.  xxvi.  532 ;  xxvii.  498  ;  Gundelach,  ibid.  xxvi.  43. 
Radziszewski  and  Wispek,  Ber.  Deutsch.Chem.  Ges.  xv.  1743  ;  xviii.  1279. 

6  Schramm,  ibid,  xviii.  1272. 

7  Colson,  Bull.  Soc.  Chim.  xliii.  6  ;  Ann.  Chim.  Phys.  [6]  vi  115. 


412  AROMATIC  COMPOUNDS. 

Metaxylyl  acetate,  CH3.C6H4.CH2O.CO.CH3,  was  prepared  by 
Volrath  by  heating  the  chloride  obtained  from  tar-xylene  with 
silver  acetate.1  Radziszewski  and  Wispek  then  prepared  it  from 
the  pure  bromide.  It  is  a  liquid  which  boils  at  226°  and  possesses 
an  aromatic  odour  resembling  that  of  apples. 

Paraxylyl  alcohol  was  obtained  by  Cannizzaro  from  paratolu- 
aldehyde  by  the  action  of  alcoholic  potash,  and  was  named 
toluenyl  alcohol.  It  crystallizes  in  white  needles,  and  is  slightly 
soluble  in  cold,  more  readily  in  hot  water,  from  which  it  sepa- 
rates in  oily  drops  which  solidify  to  fine  needles,  melting  at 
58 '5° — 59'5°  and  boiling  at  217°.  Hydrochloric  acid  converts  it 
into  the  liquid  chloride.2 

Paraxylyl  ethyl  ether  is  a  liquid  which  has  a  similar  smell  to 
benzyl  alcohol  and  boils  at  203°  (Radziszewski  and  Wispek). 

Xylyl  chlorides,  CH3.C6H4.CH2C1.  These  compounds  are  colour- 
less liquids. 

Melting-         Boiling- 
point,  point. 

Orthoxylyl  chloride —       197°— 199° 

Metaxylyl  chloride    . —       195°— 196° 

Xylyl  bromides,  CH3.C6H4.CH2Br. 

Orthoxylyl  bromide,  rhombic  prisms  21°      216° — 217° 

Metaxylyl  bromide,  liquid    ....  212°  — 215° 

Paraxylyl  bromide,  long  needles  .    .  35'5     218°— 220° 


XYLYLAMINES. 

These  have  been  prepared  by  heating  the  xylyl  chloride  from 
tar-xylene  with  ammonia,3  and  are  therefore  more  or  less  pure 
meta-compounds. 

Monoxylylamine,  CH3.C6H4.CH2.NH2,  is  an  oily,  alkaline  liquid 
which  boils  at  196°  and  smells  strongly  of  herring  brine ;  its 
hydrochloride  is  readily  soluble  in  water  and  alcohol,  and 
crystallizes  in  needles. 

Dixylylamine,  (CH3.C6H4.CH2)2NH,  is  a  similar  liquid,  which 
decomposes  above  210°;  its  hydrochloride  forms  white  needles, 
which  are  only  slightly  soluble  in  cold,  readily  in  hot  water  and 
alcohol. 

1  Ann.  Chem.  Pharm.  cxliv.  261.  2  Ibid,  cxxiv.  252. 

8  Jannasch,  ibid,  cxlii.  303  ;  Pieper,  ibid.  cli.  129. 


THE  TOLUALDEHYDES.  413 

Trixylylamine,  (CH3.C6H4.CH2)3N,  is  a  thick,  colourless  oil, 
which  has  a  characteristic  odour  and  a  faint  alkaline  reaction. 
The  hydrochloride  crystallizes  in  loose  groups  of  needles,  which 
are  insoluble  in  water,  but  slightly  soluble  in  cold  and  readily 
in  hot  alcohol.  It  decomposes  into  xylyl  chloride  and  dixylyl- 
amine  hydrochloride  when  heated  in  a  current  of  hydrochloric 
acid  gas. 


THE    TOLUALDEHYDES. 

2221  Chromyl  chloride  combines  with  the  xylenes,  as  with 
benzene  and  toluene,  to  form  compounds  which  are  decomposed 
by  water  with  formation  of  the  tolualdehydes.1 


3CH3.C6H4CH(OCrCl2.OH) 
3CH3.C6H4.CHO  +  2Cr03  +  Cr2(OH)6  +  6HC1. 

Orthotolualdehyde  was  first  prepared  by  boiling  orthoxylyl 
chloride  with  water  and  lead  nitrate  ;  it  is  a  yellowish,  strongly 
refractive  liquid,  which  smells  like  benzaldehyde  and  boils  at 
2000.2 

MetatolualdeJiyde  has  been  obtained  in  a  similar  manner  from 
metaxylyl  chloride  ;  3  it  possesses  a  similar  smell  and  boils  at 
199°.  It  combines  with  phenylhydrazine  to  form  metaxyli- 
denekydrazine,  CH3.C6H4.CH.N2H.C6H5,  which  crystallizes  from 
alcohol  in  thick,  yellow  prisms,  melting  at  91°. 

Orthonitrometatolualdekyde,  CH3.C6H3(N02)CHO,  is  formed 
when  the  aldehyde  is  allowed  to  drop  into  a  cold  mixture  of 
nitric  and  sulphuric  acids.  It  is  a  yellowish  liquid,  volatile  with 
steam,  and  is  converted  into  methylindigo  when  warmed  with 
caustic  soda  and  acetone.4 

Paratolualdehyde  was  prepared  by  Cannizzaro  by  the  distilla- 
tion of  a  mixture  of  calcium  formate  and  calcium  paratoluate, 
and  is  a  liquid  which  boils  at  204°  and  possesses  a  smell  re- 
sembling that  of  peppermint.5 

1  Etard,  Ann.   Chim.   Phys.   [5]  xxii.  218,   1881  ;  Bornemann,  Per.  Deutsch. 
Chcm.  Ges.  xvii.  1462. 

2  Raymann,  Bull.  Soc.  Chim.  xxvii.  498. 

3  Lauth  and  Grimaux,  ibid.  vii.  234  ;  Gundelach,  ibid.  xxvi.  44. 

4  Meister,  Lucius  and  Briining,  Ber.  Deutsch.  Chem.  Ges.  xvi.  817  ;  Bornemann, 
loc.  cit. 

5  Ann.  Chem.  Pharm.  cxxiv.  254. 


414  AKOMATIC  COMPOUNDS. 


THE  TOLUIC  ACIDS,  C6H  / 


CH3 


C(XH 


2222  Orthotoluic  acid  was  first  obtained  by  Bieber  and  Fittig 
by  oxidizing  orthox}dene  with  dilute  nitric  acid.1  It  may  also 
be  easily  prepared  from  its  nitril,  and  its  ethyl  ether  is  formed 
by  the  action  of  ethyl  chlorocarbonate  on  a  mixture  of  ortho- 
iodotoluene  and  sodium  amalgam.2  It  is  best  prepared  by 
heating  phthalide  with  phosphorus  and  hydriodic  acid  :  3 


C6H4<  +1, 

'CO  XXXOH 

It  crystallizes  in  long,  lustrous  needles,  which  melt  at  102°, 
and  are  slightly  soluble  in  cold,  more  readily  in  hot  water  and 
very  readily  in  alcohol. 

It  is  completely  burnt  by  chromic  acid  solution,  while  dilute 
nitric  acid  4  and  alkaline  permanganate  5  convert  it  into  phthalic 
acid. 

Calcium  orthotoluate,  (C8H702)2Ca  +  2H20,  crystallizes  in 
small  needles,  which  are  readily  soluble  in  water  but  only 
slightly  in  alcohol. 

Ethyl  orthololuate,  C8H702.C2H5,  is  a  liquid  which  boils  at 
219*5°,  and  has  an  aromatic  odour.6 

Orthotoluyl  chloride,  CH3.C6H4.COC1,  is  a  liquid  which  boils  at 
211°  (Ador  and  Rilliet). 

Ortlwtoluamide,  CH3.C6H4.CONH2,  crystallizes  from  boiling 
water  in  fine,  silky  needles,  melting  at  138°. 

Orthotolunitril,  CH3.C6H4.CN,  is  formed  by  the  distillation  of 
potassium  orthoxylenesulphonate  with  potassium  cyanide,7  and 
also  when  orthotolyl  mustard  oil  is  heated  for  an  hour  with 
copper  filings.8  It  is  a  colourless,  strongly  refractive  liquid 
boiling  at  203°  —  204°,  which  is  converted  into  the  amide  by 
heating  with  alcoholic  potash,  and  into  the  acid  by  concentrated 
hydrochloric  acid  at  180°—  200°. 

1  Ann.  Chem.  Phann.  clvi.  242. 

2  Kekule,  Bcr.  Dcutsch.  Chem.  Ges.  vii.  1007. 

3  Grabe,#ta.  xix.  778.  4  Weith,  ibid.  vii.  1057. 

8  Piccard,  ibid.  xii.  579.  6  Ador  and  Rilliet,  ibid.  xii.  2298. 

7  Fittig  and  Ramsay,  Ann.  Chem.  Pharm.  clxviii.  246. 

8  Weith,  Bcr.  Dcutsch.  Chem.  Ges.  vi.  418. 


THE  TOLCJIC  ACIDS.  415 

Chlororthotoluic  acids,  C6H3C1(CH3)CO2H,  are  obtained  by 
oxidizing  the  chloroxylenes  with  dilute  nitric  acid  : x 

Cl    CH3  C02H  Melting-point. 

4:2:1     compact  prisms 130° 

4:1:2     compact  prisms 166° 

3:2:1      needles 154° 

a-Bromorthotoluic  acid,  C6H3Br(CH3)C02H  (4:1:  2),  is  formed 
by  the  oxidation  of  bromorthoxylene,  and  crystallizes  from  hot 
alcohol  in  stellate  aggregates  of  flat  needles,  which  melt  at 
174°— 176°-2 

/3-Bromorthotoluic  acid  (3:1:2)  is  obtained  by  the  action  of 
bromine  on  orthotoluic  acid.  It  is  scarcely  soluble  in  cold, 
slightly  in  boiling  water,  but  readily  in  alcohol,  and  crystallizes 
in  long  needles,  melting  at  167°.3 

Nitro-orthotohdc  acids,  C6H3(NO2)(CH3)C02H.  The  first  of 
these  is  formed,  together  with  the  second,  by  the  nitration  of 
orthotoluic  acid,4  and,  together  with  the  third,  when  nitro- 
orthoxylene  is  oxidized.5  The  last  also  occurs,  according  to 
Racine,  in  the  products  of  the  nitration  of  orthotoluic  acid.6 

NO2  CHS  CO2H  Melting-point, 

a)  4    :    1     :    2     needles  or  microscopic  prisms  .    179° 

£)  6    :    1     :    2     needles 145° 

7)  4    :    2    :    1     long,  lustrous  needles  .    .    .    .    152° 

Amido-orthotoluic  acids,  C6H3(NH2)(CH3)CO2H : 
NH2CH3C02H 

a)  4    :    1     :    2     small  prisms 196° 

/3)  6    :    1     :    2     small,  lustrous  needles    .    .    .     191° 
7)  4    :    2    :    1     long,  flat  needles      .....     153° 

The  last  of  these  acids  decomposes  into  carbon  dioxide  and 
metatoluidine  when  it  is  heated  with  lime  (Jacobsen). 

Sulphorthotoluic  acid,  C6H3(SO3H)(CH3)CO2H  (1:2:  3),  is 
obtained  by  heating  orthotoluic  acid  to  160°  with  sulphuric 

1  Kriiger,  Ber.  Dcutsch.  Chem.  Ges.  xviii.  1755. 

2  Jacobsen,  ibid,  xvii.  2372. 

3  Jacobsen  and  Wierss,  ibid.  xvi.  1956. 

4  Fittig  and  Bieber,  Ann.  Chem.  Pharm.  cxlvi.  245  ;  Fittig  and  Ramsay,  ibid. 
clxviii.  250  ;  Jacobsen  and  Wierss,  Ber.  Deutsch.  Chem.  Gfes.  xvi.  1956. 

5  Jacobsen,  ibid.  xvii.  162. 

6  Ibid,  xviii.  3450. 


416  AROMATIC  COMPOUNDS. 

acid ;  it  forms  a  fibrous  crystalline  mass,  which  dissolves  readily 
in  water,  but  only  slightly  in  dilute  sulphuric  acid. 

Disulphorthotoluic  acid,  C6H2(SO3H)2(CH3)COaH,  is  formed 
when  orthotoluic  acid  is  heated  to  170°  with  disulphuric  acid; 
it  forms  microscopic  needles,  which  are  extremely  soluble  in 
water  (Jacobsen  and  Wierss). 

Parasulphamido-orthotoluic  acid,  C6H3(S02.NH2)(CH3)C02H 
(4:2:1),  is  formed,  together  with  the  following  compound, 
when  orthoxylenesulphamide  is  oxidized  with  an  alkaline  solution 
of  potassium  permanganate.  It  is  slightly  soluble  in  cold,  readily 
in  hot  water,  and  crystallizes  in  long  needles,  which  melt  at  217°. 
Its  potassium  salt  crystallizes  in  large,  compact  rhombohedra. 

Metasulphamido-orthotoluic  acid  (4  :  1  :  2)  is  less  soluble  in 
hot  water  than  the  isomeric  acid,  and  forms  long,  brittle  needles, 
melting  at  243°.  Its  potassium  salt  is  extremely  soluble,  and 
can  only  be  obtained  in  a  crystalline  state  by  exposing  its 
concentrated  solution  over  sulphuric  acid  for  a  long  time.1 

2223  Metatoluic  acid  is  obtained  by  the  oxidation  of  metaxy- 
lene  with  nitric  acid 2  or  potassium  permanganate.3  Richter 
prepared  it  from  orthonitrotoluene  by  converting  this  into 
bromometatolunitril  by  heating  with  alcohol  and  potassium 
cyanide  (p.  217),  and  treating  the  acid  obtained  from  this  with 
sodium  amalgam  and  water.4  It  has  also  been  obtained  from 
mesitylene,  or  symmetric  trimethylbenzene,  by  oxidizing  this 
to  uvitic  acid,  C6H3(CH3)(CO2H)2,  and  heating  the  calcium  salt 
of  the  latter  with  half  its  weight  of  slaked  lime  to  above  the 
melting-point  of  lead.5 

In  order  to  prepare  it,  metaxylene  is  heated  to  130° — 150°  for 
one  or  two  days  with  a  mixture  of  one  volume  of  nitric  acid  and 
two  volumes  of  water,  and  the  product  distilled  with  steam,  isoph- 
thalic  acid  and  nitro-compounds  being  left  behind  (Bruckner). 

Metatoluic  acid  is  more  readily  soluble  in  water  than  its 
isomerides,  and  crystallizes,  when  its  solution  is  rapidly  cooled, 
in  long,  fine  needles,  while  it  is  deposited  on  gradual  evaporation 
in  clear,  well-formed  prisms.  It  melts  at  108° — 109°,  and  readily 
sublimes. 

Calcium  metatoluate,  (C8H7O2)2Ca  +  3H2O,  crystallizes  in  aggre- 
gates of  lustrous  needles,  similar  to  those  of  calcium  benzoate. 

1  Jacobsen,  Ber.  Deutsch.  Chcm.  Gcs.  xiv.  38. 

2  Ahrens,  Zcitschr.   Chcm.  1869  ;  106  ;  Tawildarow,  Ber.  Deutsch.   Chein.  Ges. 
iv.  410  ;  Bruckner,  ibid.  ix.  405.  3  Schrbtter,  KekuUs  Org.  Chcm.  iii.  701. 

4  Ber.  Deutsch.  Chem.  Gcs.  v.  424.        6  Bottinger  and  Ramsay,  ibid.  ix.  405. 


NITROMETATOLUIC  ACIDS.  417 

Ethyl  mctatoluatc,  C8H7O2.C2H5,  is  a  liquid,  which  boils  at 
224-5°— 226-50.1 

Metatoluyl  chloride  boils  at  218°  (Ador  and  Rilliet). 

Mctatolunitril,  C6H4(CH3)CN,  has  been  obtained  by  heating 
metatolyl  mustard  oil  with  copper  dust  as  a  liquid  which 
smells  like  benzonitril,  and  is  converted  into  metatoluic  acid  by 
heating  with  concentrated  hydrochloric  acid  to  180° — 2000.2 

Chlorometatoluicacid,  C6H3C1(CH3)CO2H  (4:3:  1),  is  formed 
by  boiling  a-chlorometaxylene  with  chromic  acid,3  as  well  as  by 
replacing  the  amido-group  of  amidometatoluic  acid  by  chlorine.4 
It  is  only  very  slightly  soluble  in  water,  and  sublimes  in  dazzling 
white  needles,  which  melt  at  209°— 210°. 

a-Bromometatoluic  acid,  C6H3Br(CH3)C02H  (4:3:  1),  is 
obtained  by  the  oxidation  of  bromometaxylene  5  and  of  a-bromo- 
isocymene,6  as  well  as,  together  with  the  /3-acid,  by  the  bromina- 
tion  of  metatoluic  acid.7  It  separates  from  hot  alcohol  as  a 
crystalline  powder  or  in  small  thick  prisms,  which  melt  at 
209°— 210°. 

ft-Bromometatoluic  acid  (4:1:3)  is  formed  by  the  oxidation 
of  /3-bromo-isocymene,  and  separates  from  hot  glacial  acetic  acid 
as  a  faintly  lustrous,  crystalline  powder,  melting  at  152° — 1530.8 

Nitrometatoluic  acids,  C6H3(N02)(CH3)C02H.  Two  of  these 
are  formed  by  the  nitration  of  metatoluic  acid,9  and  both  the 
others  by  the  oxidation  of  the  corresponding  nitrometaxylene,10 
while  the  third  has  also  been  obtained  by  the  oxidation  of  nitro- 
isocymene  : n 

NO2  CH3  CO2H  Melting-point. 

a)  4     :    1     :    3     compact  prisms  ......     219° 

/?)  2    :    1     :    3     compact  prisms 182° 

7)  6     :    1     :    3     lustrous  needles  or  crystalline 

powder      .    .        214° 

8)  5    :    1     :    3     silky  needles 167° 

1  Ador  and  Rilliet,  Bcr.  Deutsch.  Chem.  Gcs.  xii.  2300. 

2  Weith  and  Landolt,  ibid,  viii.  719. 

3  Volrath,  Ann.   Chem.   Pharm.  cxliv.   266  ;  Jacobsen,  Ber,  Deutsch.  Chem. 
Ges.  xviii.  1760. 

4  Beilstein  and  Kriisler,  Ann.  Chem.  Pharm.  cxliv.  181. 

5  Fittig,  Ahrens  and  Mattheides,  ibid,  cxlvii.  32. 

6  Kelbe,  Ber.  Deutsch.  Chem.  Ges.  xv.  39. 

7  Jacobsen,  ibid.  xiv.  2351. 

8  Kelbe  and  Czarnomski,  Ann.  Chem.  Pharm.  ccxxxv.  291. 

9  Jacobsen,  Ber.  Deutsch.  Chem.  Ges.  xiv.  2353. 

10  Kreusler  and  Beilstein,  loc.  cit.  ;  Remsen  and  Kuhara,  Amer.  Chem.  Journ. 
iii.  424  ;  Thol,  Ber.  Deutsch.  Chem.  Ges.  xviii.  359. 

11  Kelbe  and  A\rarth,  Ann.  Chem.  Pharm.  ccxxi.,161. 


418  AROMATIC  COMPOUNDS. 

Amidometatoluic  acids,  C6H./NH2)(CH3)CO2H,  have  been 
prepared  by  the  reduction  of  the  first  three  nitro-acids  with  tin 
and  hydrochloric  acid : 

Melting-point. 
NH2  CH3  C02H 
a)  4    :    1     :    3     long,  thin,  colourless  plates    .     172° 

/3)  2    :    1     :    3     small,  flat  prisms 132° 

7)  6    :    1     :    3     long  needles 167° 

a-Sulphamidomctatoluic  acid,  C6H3(SO2.NH2)(CH3)C02H 
(4:3: 1),  is  formed  when  a-metaxylenesulphamide  is  oxidized 
with  chromic  acid  or  potassium  permanganate ;  it  crystallizes 
from  hot  water  in  long  needles,  melting  at  2540.1 

v-Sulphamidometatoluic  acid  (2:3:1)  has  been  obtained  by 
the  oxidation  of  v-metaxylenesulphamide,  and  forms  crystals 
which  melt  at  202°— 203°  (Jacobsen). 

2224  Paratoluic  acid  was  prepared  by  Noad  in  1847  by  the 
oxidation  of  cyrnene,  CH3.C6H4.C3H7,  with  nitric  acid ; 2  it  is 
formed  in  this  way  from  many  other  hydrocarbons  which  con- 
tain two  side-chains  in  the  para-position,  such  as  paramethyl- 
ethylbenzene,3  paraxylene,4  &c.  The  latter  is  also  converted 
into  the  acid  by  the  action  of  potassium  permanganate 5  and  of 
chromyl  chloride.6  Oil  of  turpentine  and  its  isomerides,  which 
must  be  looked  upon  as  dihydroxycymenes,  and  various  deriva- 
tives of  these  are  also  oxidized  to  paratoluic  acid  by  dilute  nitric 
acid.7  Kekule  obtained  it  synthetically  by  the  action  of  carbon 
dioxide  on  a  mixture  of  sodium  and  parabromotoluene,8  while 
Wurtz  obtained  the  ethyl  ether  by  employing  ethyl  chloro-car- 
bonate.9  It  has  also  been  synthetically  prepared  by  many  of 
the  reactions  previously  mentioned  (Part  III.,  p.  30). 

The  cymene  which  is  contained  in  Roman  cumin  oil  and  which 
can  easily  be  obtained  from  camphor,  is  employed  as  the  starting 
point  in  the  preparation  of  the  acid.  It  is  heated  for  a  con- 
siderable time  in  an  apparatus  connected  with  an  inverted  con- 
denser with  a  mixture  of  1  vol.  of  nitric  acid  of  spec.  gr.  T38 

1  lies  and  Remsen,   Ber.  Deutsch.   Chem.    Ges.   x.    1044  ;  xi.    229   and   88 ; 
Jacobsen,  ibid.  xi.  895  ;  Coale  and  Remsen,  Amer.  Chem.  Journ.  iii.  205. 

2  Chem.  Soc.  Mem.  iii.  425. 

3  Jannasch  and  Dieckmann,  Ber.  Deutsch.  Chem.  Ges.  vii.  1514. 

*  Yssel  de  Schepper  and  Beilstein,  Ann.  Chem.  Pharm.  oxxxvii.  306. 
s  Berthelot,  Bull.  Soc.  Chim.  vii.  134. 

6  Carstanjen,  Ber.  Deutsch.  Chem.  Ges.  ii.  635. 

7  Hirzel,  Zeitschr.  Chew.  1866,  205  ;  Miclk,  Ann.   Clicm.  Pharm.  clxxx.  49  J 
Hempel,  ibid,  clxxx.  74  ;  Kcibig,  ibid.  cxcv.  106. 

8  Ibid,  cxxxvii.  184.  »  Ibid.  Suppl.  vii.  127. 


PARATOLUIC  ACID.  419 


and  4  vols.  of  water,  then  neutralized  with  caustic  soda  and 
boiled  in  order  to  remove  unattacked  cymene  and  nitro-products. 
It  is  then  precipitated  with  hydrochloric  acid  and  the  precipitate 
freed  from  nitroparatoluic  acid,  &c.,  by  boiling  with  tin  and 
hydrochloric  acid.  The  product  always  contains  terephthalic 
acid,  which  remains  behind  on  treatment  with  water.  The 
paratoluic  acid  is  finally  purified  by  distillation  with  steam.1 

It  crystallizes  in  needles,  which  are  slightly  soluble  in  cold, 
more  readily  in  hot  water,  and  very  readily  in  alcohol  and  ether; 
it  melts  at  180°,  boils  at  274°— 2750,2  and  is  readily  volatile  with 
steam.  It  is  converted  into  terephthalic  acid  by  oxidation. 

All  its  salts  are  soluble  in  water. 

Calcium  paratoluate,  (C8H7O2)2Ca  +  3H2O,  crystallizes  from 
hot  water  in  dazzling  white  needles,  which  resemble  those  of 
calcium  benzoate. 

Methyl  paratoluate,  C8H702.CH3,  forms  crystals  which  have  a 
very  pleasant,  penetrating  odour;  it  melts  at  32°  and  boils  at 
217°  (Fischli). 

Ethyl  paratoluate,  C8H7O.2.C2H5,  is  a  liquid,  which  boils  at 
228°,  has  a  bitter  taste  and  a  smell  resembling  that  of  ethyl 
benzoate  (Noad). 

Phenyl  paratoluate,  C8H7O2.C6H5.  When  paratoluyl  chloride 
is  heated  with  sodium  salicylate,  a  viscid  mass  of  paratoluyl- 
salicylic  acid,  CH3.C6H4CO.OC6H4.C02H,  resembling  turpentine, 
is  formed  and  decomposes  into  phenyl  paratoluate  and  carbon 
dioxide  on  distillation  with  lime.  It  forms  white  plates,  which 
have  a  nacreous  lustre,  smell  like  the  geranium  and  melt  at 
71°— 72°.3 

Paratoluyl  chloride,  CH3.C6H4.COC1,  is  a  strongly  refractive 
liquid,  boiling  at  218°. 4 

Paratoluamide,  CH3C6H4.CO.NH2,  crystallizes  from  hot  water 
in  needles  or  plates,  which  melt  at  151°  (Fischli). 

Paratoluylamido-acetic  acid,  CH3.C6H4.CO.NH.CH2.C02H, 
which  is  also  called  toluric  acid,  occurs  in  the  urine  after  the 
administration  of  paratoluic  acid.  It  is  slightly  soluble  in  cold, 
readily  in  hot  water  and  alcohol,  and  crystallizes  in  nacreous 
plates  or  rhombic  tablets,  which  melt  at  1GO° — 165°,  and  are 

1  Dittmar  and  Kekule,  Ann.  Chcm.  Pharm.  clxii.  339 ;  Bruckner,  ibid.  ccv. 
113. 

2  Fischli,  Bcr.  Deutsch.  Chcm.  Ges.  xii.  615. 

3  Kraut,  Chem.  Centralbl.  1859,  84. 

*  Cahours,  Ann.  Chem.  Pharm.  cviii.  316  ;  Bruckner,  ibid.  ccv.  114  ;  Ador 
and  Rilliet,  Ber.  Dcutsch.  Chcm.  Ges.  xii.  2298. 


420  AROMATIC  COMPOUNDS. 

decomposed  into  paratoluic  acid  and  amido-acetic  acid  by  con- 
tinued boiling  with  hydrochloric  acid.1 

Schultzen  and  Naunyn,  after  taking  coal-tar  xylene,  found  in 
the  urine  a  toluric  acid,  which  did  not  crystallize  but  was  only 
obtained  as  a  colourless  liquid ; 2  this  substance  probably  con- 
sists entirely  or  chiefly  of  the  meta-compound. 

Paratolunitril,  CH3.C6H4.CN,  is  best  prepared  by  distilling 
paratoluic  acid  with  potassium  thiocyanate  (Part  III.,  p.  197). 
It  is  a  powerfully  refractive  liquid,  smelling  like  benzonitril, 
boils  at  217'8°  and  solidifies  at  a  low  temperature  to  a  mass, 
which  melts  at  28'5°.3 

Chloroparatoluic  acid,  C6H3C1(CH3)CO2H  (3:4: 1),  is  formed 
by  the  oxidation  of  chlorocymene,  C6H3C1(CH3)C3H7,  with  dilute 
nitric  acid.4  It  is  slightly  soluble  in  hot  water,  readily  in  alcohol, 
and  crystallizes  in  large  plates  melting  at  194° — 196°. 

a-  Bromoparatoluic  acid,  C6H3Br(CH3)CO2H  (3:4:  1),  has  been 
obtained  by  the  oxidation  of  orthobromocymene,5  bromethyl- 
methylbenzene,6  and  bromoparaxylene,7  and  is  also  formed  when 
paratoluic  acid  is  allowed  to  stand  in  contact  with  dry  bromine.8 
It  is  almost  insoluble  in  cold,  slightly  soluble  in  hot  water  and 
readily  in  alcohol,  crystallizing  in  needles,  which  melt  at  204°. 

(3 -Bromoparatoluic  acid,  which  is  formed  by  the  oxidation  of 
metabromocymene,  crystallizes  from  alcohol  in  plates  melting  at 
1960,9 

Dibromoparatoluic  acid,  C6H2Br2(CH3)C02H  (3:6:4:1),  is 
obtained  by  oxidizing  solid  dibromoparaxylene  with  a  solution 
of  chromium  trioxide  in  acetic  acid.  It  is  only  very  slightly 
soluble  in  water,  and  crystallizes  from  alcohol  in  stellate 
aggregates  of  needles,  which  melt  at  1950.10 

lodoparatoluic  acid,  C6H3I(CH3)C02H,  was  obtained  by  Griess 
together  with  amidoparatoluic  acid,  by  the  action  of  hydriodic 
acid  on  diazo-amidotoluic  acid,  it  is  slightly  soluble  in  water, 
readily  in  alcohol,  and  crystallizes  in  white,  plates  or  needles. 

1  Kraut,  Ann.  Chem.  Phrt.rm.  xcviii.  360. 

2  Zeitschr.  Chem.  1868,  29. 

3  Paterno  and  Pisati,  JSor.   Deutsch.  Chem.    Ges.  viii.  441  ;  see  also  Volrath, 
ZeUschr.   Chem.   1866,   489  ;  Hofmann,   Ann.  Chem.   Pharm.  oxlii.  126  ;  Merz, 
Zeitschr.  Chem.  1868,  33  ;  Weith,  Ber.  Deutsch.  Chem.  Ges.  vi.  421. 

4  Kekule  and  Fleischer,  ibid.  vi.  1090  ;  v.  Gerichten,  ibid.  x.  1250  ;  xi.  368. 

6  Landolph,  Bcr.  Deutsch   Chem.  Ges.  v.  268. 
e  Fittica,  Ann.  Chem.  Fharm.  clxxii.  312. 

7  Morse  and  Remsen,  Ber.  Deutsch.  Chem.  Ges  xi.  225. 

8  Jannasch  and  Dieckmann,  Ann.  Chem.  Pharm.  clxxi.  83. 

9  Kelhe  and  Koschnitzky,  ibid.  xix.  1730. 
i0  Schultz,  ibid,  xviii.  1762. 


NITROPARATOLUIC  ACIDS.  421 

a-Nitroparatoluic  acid,  C6H3(NO2)(CH3)CO2H  (3:4:1),  is 
formed  by  the  action  of  fuming  nitric  acid  on  cymene  1  or 
paratoluic  acid.2  It  is  slightly  soluble  in  cold,  more  readily  in 
hot  water  and  readily  in  alcohol,  from  which  it  crystallizes  in 
light  yellow,  monoclinic  prisms,  which  melt  at  189°  —  190°. 

(S-Nitroparatoluic  acid  (2  :  4  :  1)  is  obtained  by  the  oxidation 
of  liquid  nitrocymene  with  chromic  acid  solution  (Landolph, 
Fittica).  It  is  scarcely  soluble  in  cold,  slightly  in  hot  water,  and 
only  with  difficulty  in  alcohol,  crystallizing  in  small  plates  or 
needles,  which  sublime  without  melting  when  heated.  Accord- 
ing to  Widmaii  and  Bladin,  the  so-called  liquid  nitrocymene 
consists  chiefly  of  paratolylmethylketone,3  and  the  acid  prepared 
from  it  is  therefore  probably  not  a  nitrotoluic  acid. 

ft-Nitroparatolunitril,  C6H3(NO2)(CH3)CN,  is  obtained  by 
heating  the  diazo-compound  of  metanitroparatoluidine  with 
potassium  cuprocyanide  ;  it  melts  at  99°  —  100.°  4 

a-Amidoparatoluic  acid,  C6H3(NH2)(CH3)CO2H  (3:4:1),  is 
tolerably  soluble  in  water  and  crystallizes  in  hair-like  needles, 
which  melt  at  164°—  165°  (Ahrens). 


C02H,  is  formed  by  the  action  of  nitrogen  trioxide  on  an  alcoholic 
solution  of  the  amido-acid.  It  forms  yellow  microscopic  prisms, 
which  are  insoluble  in  water  and  alcohol,  and  is  decomposed  by 
the  haloid  acids  with  formation  of  substituted  toluic  acids.5 

Sulphoparatoluic  acid,  C6H3(SO3H)(CH3)CO2H  (2:1:  4),  has 
been  prepared  by  the  action  of  sulphur  trioxide  on  paratoluic 
acid,6  and  by  the  oxidation  of  thiocymene,  C6H3(SH)(CH3)C3H7  7 
and  cymene-orthosulphonic  acid.8  It  crystallizes  in  small  plates 
which  contain  two  molecules  of  water  and  are  stable  in  the  air. 

Sulphamidoparatoluic  acid,  C6H3(S02.NH2)(CH2)CO2H,  is 
formed  by  the  oxidation  of  paraxylenesulphamide  9  or  cymene- 
sulphamide,10  and  crystallizes  from  hot  water  in  long  needles 
which  melt  at  1670.11 

1  Noad,    Chem.    Soc.    Mem.  iii.    431  ;   Ahrens,    Zeitschr.    Cham.    1869,    102  ; 
Landolph,  Ber.  Deutsch.  Chem.  Ges.  vi.  936  ;  Fittica,  ibid.  vi.  938. 

2  Ann.  Chem.  Pharm.  clxviii.  250.         3  Ber.  Deutsch.  Chem.  Ges.  xix.  584. 

4  Leukart,  ibid.  xix.  417.  5  Griess,  Ann.  Chem.  Pharm.  cxvii.  58. 

6  Fischli,  Ber.  Deuttch.  Chem.  Ges.  xii.  615. 

7  Flesch,  ibid.  vi.  478  ;  Bechler,  Journ.  PraU.  Chem.  [2]  viii.  170. 

8  Remsen  and  Burney,  Amer.  Chem.  Journ.  ii.    405  ;  Baur  and  Meyer,  Ann. 
Chem.  Pharm.  ccxx.  18. 

9  Ahrens,    Zeitschr.    Chem.    1869,  102  ;  Landolph,  Ber.  Deutsch.   Chem.  Ges. 
vi.  936  ;  Fittica,  ibid.  vi.  938. 

10  Ann.  Chem.  Pharm.  clxviii.  250. 

11  lies  and  Remsen,  Ber.  Deutsch.  Chem.  Ges.  xi.  230  ;  Hall  and  Remsen,  ibid. 
xii.  1433. 

258 


422  AROMATIC  COMPOUNDS. 


HYDROXYTOLUALDEHYDES,  C6H4(OH)(CH3)COH. 

2225  These  compounds  are  formed  when  the  cresols  are 
heated  with  caustic  soda  solution  and  chloroform,  homosalicyl- 
aldehydes  being  formed,  which  are  volatile  with  steam.  Ortho- 
and  meta-cresol  also  yield  homologues  of  parahydroxybenz- 
aldehyde,  which  are  not  volatile  with  steam,  but  this  is  not  the 
case  with  paracresol,  since  in  the  chloroform  reaction  the  alde- 
hyde-group always  takes  up  either  the  ortho-  or  para-position 
with  respect  to  the  hydroxyl.1 

Parahomosalicylaldehyde  or  Orthohydroxymetatohialdehyde 
(COH :  OH  :  CH3  =  1  :  2  :  5)  is  slightly  soluble  in  water,  readily 
in  alcohol,  and  crystallizes  from  dilute  alcohol  in  six-sided  plates 
which  have  a  nacreous  lustre,  and  melt  at  56°.  It  boils  at 
217° — 218°,  has  a  powerful,  almost  repulsive  aromatic  odour,  and 
gives  a  deep  blue  colouration  with  ferric  chloride. 

It  is  converted  by  the  action  of  water  and  sodium  amalgam 
into  homosaligenin  or  ortlwhydroxymetaxylyl  alcohol,  C6H3(OH) 
(CH3)CH2.OH,  which  crystallizes  from  hot  water  in  lustrous 
plates,  melts  at  105°  and,  like  saligenin,  gives  a  deep  blue 
colouration  with  ferric  chloride. 

OrtJiohomosalicylaldehyde  or  Orthohydroxymetatolualdehyde  (1  : 
2  : 3)  is  an  oily  liquid,  which  has  a  smell  resembling  both  salicyl- 
aldehyde  and  oil  of  bitter  almonds,  solidifies  on  cooling  to 
crystals  which  melt  at  17°,  and  gives  a  bluish  colouration  with 
ferric  chloride. 

Metahomosalicylaldehyde  or  Orthohydroxyparatolnaldehyde  (1  : 
2  : 4)  forms  crystals,  which  melt  at  54°  and  have  a  pleasant 
aromatic  odour.  It  boils  at  222° — 223°  and  gives  a  violet 
colouration  with  ferric  chloride, 

Orthohomoparahydroxylenzaldeliyde  or  Parahydroxymetatolu- 
aldehyde  (1:4:3)  crystallizes  from  hot  water  in  pointed  prisms, 
which  occur  chiefly  in  twinned  forms,  resembling  gypsum.  It 
melts  at  115°  and  gives  a  bluish  violet  colouration  with  ferric 
chloride. 

Metahomopardhydroxybenzaldehyde  or  ParahydroxyortTiotolu- 
aldehyde  (1:4:2)  crystallizes  in  lustrous  plates,  melts  at  110° 
and  gives  a  light  rose-red  colouration  with  ferric  chloride. 

1  Tiemann  and  Schotten,  Bcr.  Dcutsch.  Chem.  Ges.  xi.  770. 


HYDROXYTOLUIC  ACIDS.  423 

Menyanthol,  G8H8O.  An  amorphous  substance,  called  meny- 
anthin,  C30H46O14,  which  has  an  intensely  bitter  taste,  occurs  in 
the  common  buckbean  (Menyanthes  trifoliata)  and  is  decom- 
posed by  heating  with  dilute  sulphuric  acid  into  grape  sugar 
and  menyanthol.  This  substance  is  a  liquid  which  smells  like 
benzaldehyde,  reduces  ammoniacal  silver  solution,  and  is  con- 
verted into  a  crystalline  acid  on  exposure  to  the  air  or  on  fusion 
with  caustic  potash.1  It  is  probably  identical  with  orthohomo- 
salicylaldehyde. 


HYDROXYTOLUIC  ACIDS,  C6H3(OH)(CH3)C02H. 

2226  Kolbe  and  Lautemann,  after  finding  that  salicylic  acid  is 
formed  by  the  action  of  carbon  dioxide  on  a  mixture  of  phenol  and 
sodium,  prepared  its  homologue,  cresotic  acid,  from  the  cresol 
which  boils  at  1200.2  The  three  cresotic  acids  were  then  pre- 
pared from  the  isomeric  cresols,3  and,  on  account  of  their 
similarity  to  salicylic  acid,  were  also  called  homosalicylw  acids. 
Ihle  has  shown  that,  like  their  lower  homologue,  they  may 
be  obtained  by  passing  carbon  dioxide  over  the  heated  sodium 
cresols.4 

These  compounds  and  the  other  hydroxytoluic  acids,  the  ten 
of  which  are  all  known,  are  also  formed  by  reactions  similar  to 
those  employed  for  the  preparation  of  the  hydroxybenzoic  acids 
and  other  hydroxy-acids  (Part  III.,  p.  32). 

The  dimethyl  ethers,  C6H3(CH3)(OCH3)CO2.CH3,  are  formed 
by  heating  the  acids  with  caustic  potash  and  methyl  iodide,  and 
these  are  converted  by  saponification  into  the  methoxytoluic 
acids,  C6H3(CH3)(OCH3)CO2H.5 

The  numbers  appended  in  brackets  give  the  position  of  the 
side  chains  in  the  order  C02H  :  OH :  CH3. 

Parahomosalicylic  acid,  a-Cresotic  acid  or  a-OrtJiohydroxymeta- 
toluic  add  (1:2:5),  may  be  obtained,  in  addition  to  the  methods 
just  described,  by  fusing  ^-metaxylenol 6  or  /3-bromometatoluic 
acid 7  with  caustic  potash,  by  the  action  of  nitrous  acid  on  the 

Kromayer,  Jahresb.  Chem.  1861,  749. 
Ann.  Chem.  Pharm,.  cxv.  203. 

Engelhardt  and  Latschinow,  Zeitschr.   Chem.   1869,   622  ;  Biedermann,  Ber. 
Deutsch.  Chem.  Ges.  vi.  325  ;  Kekule,  ibid.  vii.  1006. 
Journ.  Prakt.  Chem.  [2]  xiv.  454. 
Schall,  Ber.  Deutsch.  Chem.  Ges.  xii.  822. 
Jacobsen,  ibid.  xi.  374.  7  Ibid.  xiv.  2347. 


424  AROMATIC  COMPOUNDS. 

amidometatoluic  acid  which  melts  at  1720,1  and  by  heating  para- 
cresol  with  caustic  soda  and  tetrachloromethane.2  It  crystallizes 
from  hot  water  in  very  long  needles  or  rhombic  prisms,  melting 
at  151°,  and  is  readily  volatile  with  steam.  Its  aqueous  solution 
is  coloured  an  intense  violet-blue  by  ferric  chloride ;  it  decom- 
poses into  paracresol  and  carbon  dioxide  when  heated  to  180° 
with  hydrochloric  acid,  while  a  remarkable  reaction  occurs  when 
its  calcium  salt  is  heated  with  lime,  orthocresol  being  formed 
(Jacobsen). 

Methylparahomosalicylic  acid  forms  long,  thin  needles,  melting 

at  67°. 

Orthohomosalicylic  acid,  j3-Cresotic  acid,  or  v-OrtTioTiydroxymeta- 
toluic  acid  (1 : 2  : 3)  is  also  formed  by  fusing  v-sulphamidometa- 
toluic  acid  with  caustic  potash  3  and  by  the  action  of  nitrous 
acid  on  the  amidometatoluic  acid  melting  at  132°  (Jacobsen). 
It  crystallizes  from  hot  water  in  long,  flat  needles,  which  melt  at 
163°— 164°.  It  decomposes  into  orthocresol  and  carbon  dioxide 
when  heated  with  hydrochloric  acid  to  210° ;  ferric  chloride 
colours  its  aqueous  solution  deep  violet. 

Methylorthoh&niosalicylic  acid  crystallizes  in  feathery  needles 
and  melts  at  81°. 

a-Metaliomosalicylic  acid,  y-Oresotic  acid,  or  Orthohydroxypara- 
tduic  acid  (1 : 2  :  4)  is  also  obtained  by  fusing  paraxylenol  with 
caustic  potash  (Jacobsen),  and,  together  with  metahomopara- 
hydroxybenzoic  acid,  when  metacresol  is  heated  with  tetrachloro- 
methane and  caustic  soda  (Schall).  It  crystallizes  from  water 
in  needles  and  from  alcohol  in  monoclinic  prisms,  which  melt  at 
1770,4  and  are  volatile  with  steam.  On  heating  with  hydro- 
chloric acid  to  170°,  it  decomposes  into  metacresol  and  carbon 
dioxide  ;  ferric  chloride  produces  a  deep  violet  colouration  in  its 
aqueous  solution. 

a-Methylmeiahomosalicylic  acid  crystallizes  in  plates,  which 
melt  at  103°— 104°. 

/3-Metahomosalicylic  acid  (1:2:6)  has  been  obtained  from 
/3-bromorthotoluic  acid.  It  is  slightly  soluble  in  cold,  readily 
in  hot  water,  very  freely  in  alcohol,  crystallizes  in  long 
needles,  melting  at  1(58°,  and  is  tolerably  volatile  with  steam. 
Its  solution  is  coloured  a  deep  blue-violet  by  ferric  chloride; 

1  Ber.  Deutsch.  Chcm.  Ges.  xiv.  2352.  ;  Panaotovi6,  Journ.  PraU.  Cliem.  [2] 
xxxiii.  63.  2  Schall,  ibid.  xii.  821. 

3  Ber.  Deutsch.  Chcm   Ges.  xi.  902. 

4  Oppenheimer  and  Pfiiff,  ibid.  viii.  889. 


PARAHOMOMETAHYDROXYBENZOIC  ACID.  425 

on   heating  to    200°   with    concentrated    hydrochloric    acid,   it 
decomposes  into  metacresol  and  carbon  dioxide.1 

2227  Parahomometahydroxy~benzoic  acid  or  Metahydroxyortho- 
toluic  acid  (1:5:  2)  is  formed  by  fusing  metasulphamido-ortho- 
toluic  acid,2  a-bromorthotoluic  acid,3  or  the  chlororthotoluic  acid 
melting  at  1660,4  with  caustic  potash,  and  from  /3-amidortho- 
toluic  acid  by  means  of  the  diazo-reaction.5  It  is  slightly 
soluble  in  cold,  readily  in  hot  water,  crystallizes  in  transparent 
prisms,  which  melt  at  172°  and  sublime  in  needles,  and  is  also 
volatile  with  steam.  Ferric  chloride,  added  to  its  cold  saturated 
solution  or  to  that  of  its  ammonium  salt,  produces  a  light 
brown  precipitate  soluble  in  a  large  quantity  of  hot  water. 
It  is  not  attacked  by  concentrated  hydrochloric  acid  even 
at  220°. 

Metahomometahydroxybenzoic  acid  or  s-Hydroxytoluic  acid 
(1:3: 5).  Fuming  sulphuric  acid  converts  metatoluic  acid  into 
two  isomeric  sulphonic  acids,  which  yield  a  mixture  of  symmetric 
hydroxymetatoluic  acid  and  parahomosalicylic  acid  on  fusion 
with  caustic  potash ;  the  latter  may  be  removed  by  distillation 
with  steam,  while  the  former  differs  from  all  its  isomerides  in 
not  being  volatile. 

Symmetric  hydroxytoluic  acid  is  tolerably  soluble  in  cold,  readily 
in  hot  water,  and  crystallizes  in  fascicular  aggregates  of  needles, 
which  melt  at  208°;  it  solidifies  to  hard,  transparent  prisms 
and  sublimes  in  stellate  groups  of  needles.  Solutions  of  the 
acid  and  of  its  salts  give  a  fawn-coloured  precipitate  with  ferric 
chloride,  which  dissolves  in  a  large  excess  of  the  reagent,  forming 
a  dark  brown  solution.  It  is  not  attacked  by  concentrated 
hydrochloric  acid  at  230°,  and  yields  metacresol  when  distilled 
with  lime.6 

s-Trinitrohydroxytoluicacid,  C6(N02)3(OH)(CH3)C02H  +  H2O 
Warren  de  la  Rue,  by  heating  the  colouring  matter  of  cochineal 
with  nitric  acid,  obtained  nitrococcusic  acid,  which  possesses  the 
same  composition  as  the  trinitro-anisic  acid  prepared  by  Cahours, 
but  is  obviously  not  identical  with  it.7  Gmelin  states  that  it  is 
isomeric  with  the  latter  and  also  with  methyltrinitrosalicylic 
acid.8  It  differs  from  both  of  these  by  being  dibasic,  and  Strecker 
on  this  account  suggested  that  it  might  be  trinitrocresotic  acid.9 

1  Jacobsen,  Per.  Deutsch.  Chem.  Ges.  xvi.  1962. 

2  Ibid.  xiv.  38.  3  Ibid.  xvii.  2375. 

4  Kriiger,  ibid,  xviii.  1758.  5  Jacobsen  and  Wierss,  ibid.  xvi.  1959. 

6  Jacobsen,  ibid.  xiv.  235.7.  7  Ann.  Chem.  Pharm.  Ixiv.  23. 

8  Handb.  Org.  Chem.  iii.  398.  9   Lehrb.  Org.  Chem.  v.  Aufl.  727. 


426  AROMATIC  COMPOUNDS. 

Liebermann  and  Dorp  found  that  it  decomposes  into  carbon 
dioxide  and  trinitrometacresol  when  heated  with  water  to  ISO0,1 
and  therefore  considered  it  to  be  a  trinitro-derivative  of  the 
then  unknown  symmetric  hydroxytoluic  acid.  After  the  dis- 
covery of  the  latter,  Kostanecki  and  Niementowski  showed  that 
on  solution  in  warm  nitric  acid  it  is  converted  into  nitrococcusic 
acid.2 

It  crystallizes  from  hot  water  in  colourless,  rhombic  plates, 
which  are  yellow  when  not  perfectly  pure,  and  form  a  yellow 
solution  in  water  which  dyes  animal  fabrics  and  the  skin  an 
intense  yellow.  It  melts  with  decomposition  between  170°  and 
180°,  and  detonates  at  a  higher  temperature.  Its  salts  are 
soluble  in  water  and  detonate  violently  on  heating. 

a-Orthohomometahydroxylenzoic  acid  or  Metakydroxyparatoluic 
acid  (1:3:4)  is  formed  by  fusing  paratolulylsulphonic  acid,3 
chloroparatoluic  acid,  bromoparatoluic  acid  4  or  sulphamidopara- 
toluic  acid5  with  caustic  potash,  as  well  as  by  the  action  of 
nitrous  acid  on  amidoparatoluic  acid.6  It  crystallizes  in  long 
needles,  melting  at  206° — 207°,  is  slightly  soluble  in  cold,  readily 
in  hot  water,  and  volatilizes  with  steam.  Ferric  chloride  gives 
no  colouration,  and  hydrochloric  acid  has  no  action  upon  it  at 
270°.  On  distillation  with  lime  it  decomposes  into  orthocresol 
and  carbon  dioxide. 

j3-0rthohomometahydroxybenzoic  acid  (1:3:2)  was  obtained  by 
Jacobsen  from  sulphorthotoluic  acid.  It  crystallizes  from  hot 
water  in  long  needles  with  a  vitreous  lustre,  which  melt  at 
183°.  are  volatile  with  steam,  and  are  not  attacked  by  hydro- 
chloric acid  at  200° — 210°.  It  yields  orthocresol  on  distillation 
with  lime.  Ferric  chloride,  added  to  an  aqueous  solution  of  the 
acid  or  one  of  its  salts,  produces  a  heavy,  bulky,  light  brown 
precipitate. 

j3-Methylorthohomometahydroxybenzoic  acid  crystallizes  in  long, 
fine  needles,  and  melts  at  1460.7 

2228  Metahomoparahydroxybenzoic  acid  or  ParahydroxyortTio- 
toluic  acid  (1:4:2)  is  obtained  by  fusing  the  aldehyde  with 
caustic  potash.8  It  is  also  formed,  together  with  a  small 
quantity  of  metahomosalicylic  acid,  when  metacresol  is  heated 

1  Ann.  Chem.  Pharm.  clxiii.  99.  2  Ber.  Deutsch.  Chem.  Gcs.  xviii.  250. 

3  Flesch,  ibid.  vi.  481.  4  v.  Gerichten,  ibid.  xi.  368. 

5  Hall  and  Remsen,  ibid.  xii.  1433. 

6  Fittica,  ibid.  vii.  927  ;  v.  Gerichten  and  Rossler,  ibid.  xi.  705. 

7  Jacobsen,  ibid.  xvi.  1962. 

8  Schrotten  and  Tiemann,  ibid.  xi.  778. 


DIHYDROXYTOLUALDEHYDES.  427 

with  tetrachloromethane  and  concentrated  caustic  soda  solution,1 
and  when  parasulphamido-orthotoluic  acid2  or  the  chlorortho- 
toluic  acid  which  melts  at  130° 3  is  fused  with  caustic  potash.  It 
crystallizes  from  hot  water  in  small  needles  which  contain  half  a 
molecule  of  water  of  crystallization ;  this  is  lost  at  100°  and 
the  anhydrous  residue  then  melts  at  177° — 178°.  Ferric  chloride 
produces  no  colouration,  but  gives  a  reddish  brown  precipitate 
with  its  salts,  which  dissolves  in  an  excess  of  the  reagent  forming 
a  dark -brown  solution.  On  heating  to  200°  with  hydrochloric 
acid  it  decomposes  into  carbon  dioxide  and  metacresol. 

Methylmetahomoparahydroxybenzoic  acid  crystallizes  in  long 
needles  and  melts  at  176°. 

Orthohomoparahydroxybenzoic  acid  or  Parahydroxymetatoluic 
acid  (1  :  4  :  3)  is  formed  by  fusing  the  aldehyde,4  a-sulphamido- 
toluic  acid 5  a-bromometatoluic  acid,6  or  chlorometatoluic  acid  7 
with  caustic  potash,  and  together  with  a  small  quantity  of 
*orthohomosalicylic  acid  by  heating  orthocresol  with  tetrachloro- 
methane and  caustic  soda  (Schall).  It  crystallizes  from  hot 
water  in  small  needles,  containing  half  a  molecule  of  water, 
which  is  lost  at  100°;  the  anhydrous  acid  melts  at  171°— 173°, 
and  is  volatile  with  steam.  Ferric  chloride  produces  no  coloura- 
tion; on  heating  with  hydrochloric  acid  to  180° — 185°  it 
decomposes  into  carbon  dioxide  and  orthocresol. 

MetJiyltyrthohomoparahydroxybenzoic  acid  forms  microscopic 
silky  needles,  melting  at  192°— 193°. 


DIHYDROXYTOLUALDEHYDES, 

C6H2(CH3)(OH)2CHO. 

2229  Para-orsellinaldeJiyde,(CTLO  :  OH  :  OH :  CH3  =  1:2:4:6). 
This  compound,  which  is  also  known  as  orcylaldehydc,  is  formed 
together  with  two  orcendialdehydes,  C6H(CH3)(OH)2(CHO)2,  by 
heating  orcinol  with  caustic  potash  and  chloroform  ;  it  crystallizes 
from  hot  water  in  fascicular  or  stellate  aggregates  of  needles, 
which  melt  at  177° — 178°.  Its  aqueous  solution  is  coloured 
reddish  brown  by  ferric  chloride.8  The  constitution  of  this  body 

1  Schall,  Bcr.  Deutsch.  Chem.  Ges.  xii.  819. 

-  Jacobsen,  ibid.  xiv.  40.  3  Kriiger,  loc.  cit. 

4  Schotten  and  Tiemann.  5  Jacobsen,  ibid.  xi.  897. 

6  Jacobsen,  ibid.  xiv.  2351.  7  Ibid,  xviii.  1760. 

8  Tiemann  and  Helkenberg,  ibid.  xii.  999. 


428  AROMATIC  COMPOUNDS. 

has  not  been  determined,  but  since  resorcinol  is  converted  by 
the  above  reaction  into  /2-resorcylaldehyde,  in  which  the  alde- 
hyde group  takes  the  para-position  with  regard  to  one  hydroxyl 
and  the  ortho-position  to  the  other,  this  is  probably  also  the  case 
with  orcylaldehyde. 

Metdhomomethoxysalicylaldehyde  (1:2:3:5)  has  been  obtained 
from  creosol  and  chloroform,  and  forms  an  oily  liquid,  which 
possesses  a  smell  resembling  that  of  salicylaldehyde,  and,  like 
the  latter,  forms  a  deep  yellow  coloured  solution  in  alkalis. 
Ferric  chloride  produces  a  deep  green  colouration.1 


DIHYDROXYTOLUIC   ACIDS,  CH3.C6H2(OH)2C02H. 

2230  In  the  year  1830,  Heeren  investigated  the  lichens 
Eocella  tinctoria  and  Lecanora  tartarea,  which  are  employed  in 
Holland  for  the  manufacture  of  litmus  and  archil,  and  found  in 
them  a  characteristic,  colourless,  crystalline  substance,  which  is 
converted  into  a  red  dye  by  the  united  action  of  air  and 
ammonia,  and  which  he  therefore  named  erythrin  (e'pvS/oo?,  red). 
On  boiling  with  a  solution  of  ammonium  carbonate,  it  was  con- 
verted into  the  amorphous  erythrinbitter.  In  order  to  obtain 
erythrin  in  larger  quantities,  he  extracted  the  lichens  with 
alcohol,  but  found  that  the  erythrin  was  thus  converted  into  a 
similar  substance,  which  was,  however,  unsuitable  for  the  pre- 
paration of  the  dye,  and  which  he  named  pscudoerythrin?  He  also 
found  rocellic  acid  in  the  lichens  which  he  examined  (Pt.  II.  p.  289). 

Kane,  however,  obtained  different  results ;  in  extracting  the 
lichens  with  hot  alcohol  he  obtained  erythrylin,  insoluble  in  water, 
and  a  soluble  crystalline  compound,  which  is  identical  with 
pseudoerythrin  and  is  not  an  accidental  product,  but  one  of  the 
most  important  of  the  whole  series.  He  therefore  transferred 
the  name  erythrin  to  this  substance  and  assumed  that  Heeren's 
erythrin  was  a  mixture  of  erythrylin  with  other  bodies.  When 
its  solution  is  exposed  to  the  air,  erythrinbitter  or  amarythrin 
is  formed,  and  this  converted  after  several  months'  exposure  into 
crystalline  tclerythrin,  to  which  he  gave  this  name  in  contradis- 
tinction to  erythrylin,  since  the  word  reXo?  denotes  the  end, 
and  v\rj  the  beginning  of  the  series.3 

1  Tiemann  and  Koppe,  Ber.  Deutsch.  Chem.  Gcs.  xiv.  2026. 

2  Schweigycr's  Journ.  lix.  313.  3  Phil.  Trans.  1840,  273. 


DIHYDROXYTOLUIC  ACIDS.  429 

Schunck  then  investigated  many  varieties  of  Lccanora  and 
Variolaria  from  the  Vogelsberg,  and  found  in  them  a  crystalline 
compound,  which,  like  Heeren's  erythrin,  is  converted  into  a  red 
dye  by  exposure  to  the  air,  but  has  a  different  composition,  and 
which  he  therefore  named  lecanorin.1  On  boiling  with  baryta 
water,  it  decomposed  into  carbon  dioxide  and  orcinol,  which  had 
already  been  prepared  from  these  species  of  lichens  by  Robiquet, 
while  on  boiling  with  alcohol  it  was  converted  into  Heeren's 
pseudoerythrin.2 

Eochleder  and  Heldt,  who  detected  lecanorin  in  Everma 
Prunastri,  showed  that  it  is  also  converted  into  pseudo- 
erythrin by  the  action  of  hydrochloric  acid  and  alcohol; 
the  latter  substance  must  therefore  be  looked  upon  as  the  ethyl 
ether  of  lecanorin,  or  as  it  is  more  suitably  called,  lecanoric 
acid.31 

This  compound  was  then  carefully  examined  by  Schunck,4 
who  also  submitted  the  substances  contained  in  Rocella  tinctoria 
var.  fuciformis  from  Madagascar  and  Angola  to  a  new  investiga- 
tion. The  most  important  of  these  is  erythric  acid,  which 
yields  the  colouring  matter.  This  is  so  readily  converted  into 
the  ethyl  ether  or  pseudoerythrin  by  boiling  with  alcohol,  that 
the  latter  is  always  obtained  when  the  lichens  are  extracted 
with  boiling  alcohol.  This  compound  has  the  same  composition 
as  ethyl-lecanoric  acid,  and  appears  to  be  identical  with  it — a 
fact  which  admits  of  the  simple  explanation  that  erythric  acid  is 
a  copulated  compound  of  lecanoric  acid  and  orcinol.  On  boiling 
with  alcohol,  orcinol  is  set  free  and  the  lecanoric  acid  combines 
with  the  ethoxyl  residue.5 

Erythric  acid  is  converted  by  boiling  with  water  into  picro- 
erythrin,  the  properties  of  which  are  not  identical  either  with 
those  of  Heeren's  erythrinbitter  or  of  Kane's  amarythrin ;  they 
approach  most  closely  to  those  of  telerythrin. 

Stenhouse,  who  investigated  a  South  American  sample  of 
Rocella  tinctoria,  found  in  it  a-orsellic  acid,  which  is  decomposed 
by  boiling  with  milk  of  lime  or  baryta  into  orcinol  and  a-orsellinic 
acid,  while  Schunck's  lichen,  which  is  E.  Montagnei,  contains 
erythric  acid,  which  yields  picroerythrin  and  erythrelinic  acid, 
which  is  very  similar  to  a-orsellinic  acid.  According  to  Schunck, 
picroerythrin  is  decomposed  by  boiling  with  an  excess  of  lime  or 

1  Ann.  Chem.  PJiarm.  xli,  157. 

2  Ibid.  xlv.  250.  3  Ibid,  xlviii.  1. 
4  Ibid.  liv.  261.                                    6  Ibid.  Ixi.  64. 


430  AROMATIC  COMPOUNDS. 

baryta  into  carbon  dioxide  and  orcinol,  but  Stenhouse  lias  shown 
that  crythroglucin  is  also  formed.1 

Stenhouse  also  discovered  a  {3-orscllic  acid  in  Eocella  tinctoria 
from  the  Cape  of  Good  Hope,  but  this  was  shown  by  Gerhardt, 
who  was  subsequently  confirmed  by  Stenhouse  himself,  to  be 
identical  with  the  a  -acid. 

In  "Remarks  on  the  Preceding  Communication,"  Strecker 
observes  :  Stenhouse  has  made  us  acquainted  with  a  series  of 
acids  which  are  of  special  interest,  both  on  account  of  their  similar 
properties  and  analogous  reactions,  and  from  the  fact  of  their 
occurrence  in  the  same  plants.  It  is  for  this  reason  desirable 
that  the  changes  undergone  by  these  compounds  should  be 
represented  by  formulae,  and  for  this  purpose  it  is  necessary  to  sub- 
stitute new  expressions  for  some  of  the  empirical  formulae  given 
by  Stenhouse,  since  the  former  agree  equally  well  with  the 
experimental  results  and  are  also  capable  of  representing  the 
decompositions  and  reactions  of  the  substances  in  question. 

a-Orsellic  acid,  then,  is  converted  into  two  molecules  of 
orsellinic  acid,  the  elements  of  water  being  taken  up  : 

C16H1407+H20  =  2C8H804. 

The  former  can  also  form  orcinol  with  loss  of  carbon  dioxide  : 
C16H1407  +  H20  =  2C7H804  +  2C02. 

The  conversion  of  orsellinic  acid  into  orcinol  takes  place  with 
the  separation  of  carbon  dioxide  : 

C8H804=C7H802+C02. 

Erythric  acid  is  resolved  into  picroerythrin  and  erythrelic 
acid,  which  is  undoubtedly  orsellinic  acid  : 


=  C12H1607  +  C8H8O4. 

Finally,  picroerythrin  decomposes  into  carbon  dioxide,  orcinol 
and  erythroglucin  : 

C12H1607  +  H20  =  C02  +  C7H802  +  C4H1004. 

He  adds  that  erythric  acid  can  yield  twice  as  much  orsellinic 
acid  as  given  by  the  equation,  but  Stenhouse  considers  this  as 
improbable.  In  this  case  the  formula  of  the  former  would  be 
C14H1507:2 

2C8H804  +  C12H807  =  2C14H1507  +  H20. 

1  Stenhouse,  Phil  Trans.  1848,  63.  2  Ann.  Chem.  Phann.  Ixviii.  108. 


ERYTHRIN  AND  PICROERYTHRIN.  431 

Gerhardt  came  to  the  conclusion  that  orsellic  acid  has  the 
formula  C16OUO7,  and  is  identical  with  lecanoric  acid,1  while 
Schunck  expressed  the  opinion  that  the  ethyl'  ether  of  orsellinic 
acid  is  identical  with  that  of  lecanoric  acid,  just  as  is  the  case 
with  erythrin  and  pseudoerythrin.2 

Hesse  then  undertook  a  new  investigation  of  these  lichen 
substances.  He  ascertained  that  the  Angola  lichen,  which 
comes  into  the  market  under  many  names,  is  Rocella  fuciformis, 
and  retained  Heeren's  name  of  erythrin  for  the  chroniogen  con- 
tained in  it,  since  it  scarcely  possesses  the  properties  of  an  acid. 
His  analysis  gave  him  results  in  accordance  with  Strecker's 
second  formula,  which,  however,  he  doubled  and  wrote  C28H30014. 
The  acid  obtained  from  it  by  decomposition  proved  as  Strecker 
had  correctly  foreseen,  to  be  identical  with  orsellinic  acid.3 

Stenhouse  confirmed  these  observations,  and  adopted  the 
same  formula  for  erythrin,  giving  equations  to  explain  its 
changes  and  decompositions,4  but,  in  spite  of  this,  Strecker's 
first  formula  has  been  shown  to  be  correct. 

After  it  had  been  recognized  that  erythroglucin  or  erythrol 
as  it  is  now  called,  is  an  alcohol,  Berthelot  suggested  that 
erythrin  is  the  orsellinic  ether  of  this,  and  de  Luynes  has 
observed  that  it  is  in  fact  the  di-acid  ether  of  this  alcohol,  picro- 
ery thriii  being  the  mono-acid  derivative.5  Orsellinic  acid  has 
proved  to  be  a  dihydroxytoluic  acid,  and  the  compounds  in 
question  have,  therefore,  the  following  constitution  : 

Erythrin : 

CH3.C6H2(OH)2CO.(\ 

>4H6(OH)2. 
CH3.C6H2(OH)2CO.(X 

Picroerythrin : 
CH3.C6H2(OH)2CO.OC4H6(OH)S. 

Further  investigations  conducted  by  Hesse  have  finally  decided 
that  the  archil  lichens  which  occur  in  commerce  consist  chiefly 
of  two  species.  Rocella  fuciformis  (Acharius)  comprises  those 
from  Lima,  Angola,  Mozambique,  Zanzibar  and  Ceylon;  this 
contains  erythrin  alone,  while  Hocella  tinctoria  (De  Candolle), 

1  Compt.  Rend.  Chim.  1849,  127.  2  Phil.  Mag.  xxxiii.  249, 

3  Ann.  Chem.  Pharm.  cxvii.  297.  4  Proc.  Roy.  Soc.  xii.  263. 

5  Ann.  Chem.  Pharm.  cxxxii.  355. 


432  AROMATIC  COMPOUNDS. 

which  comes  from  Cape  Verde  and  the  neighbouring  islands, 
contains  a  chromogen,  lecanoric  acid,1  which  is  identical  with 
orsellic  acid. 

Stenhouse  remarks  on  this  point  that  the  South  American 
lichens  examined  by  him  are  also  Rocella  tinctoria.  They  are 
sent  into  the  market  under  the  name  of  Valparaiso  lichens,  but 
are  seldom  exported  to  England,  while  the  Lima  lichens  (Rocella 
fuciforniis)  are  sent  there  in  large  quantities.2 

Lecanor;c  acid  is  monobasic  and  stands  in  the  same  relation 
to  orsellic  acid  as  glycollic  acid  to  glycoglycollic  acid  : 

/OH 
CH3.C6H2(-OH 

\CO\ 

/O  / 
CH3.C6H2^-OH 

\C02H. 

2231  Orsellinic  acid,  CH3.C6H2(OH)2C02H  +  H2O,  is  readily 
prepared  from  erythrin  by  heating  it  on  the  water  bath  with 
baryta  water  until  barium  carbonate  commences  to  separate.  A 
few  drops  of  the  solution  are  then  tested  with  hydrochloric  acid 
at  short  intervals,  and  as  soon  as  a  gelatinous  precipitate  is 
no  longer  formed,  hydrochloric  acid  is  added  to  the  solution, 
the  orsellinic  acid  being  thus  soon  precipitated.  It  crystal- 
lizes from  acetic  acid  in  stellate  aggregates  of  needles,  and 
separates  from  dilute  alcohol  as  a  crystalline  mass,  which  is 
readily  soluble  in  water,  becomes  anhydrous  at  100°,  and  melts 
at  176°,  a  gradual  decomposition  into  carbon  dioxide  and  orcinol 
accompanied  by  violent  frothing,  taking  place.  The  same 
decomposition  occurs  on  boiling  with  water  or  alkalis.  Its 
aqueous  solution  is  coloured  purple-violet  by  ferric  chloride,  and 
gives  an  amorphous  precipitate  with  an  ammoniacal  solution  of 
lead  acetate. 

Barium  orsellinate,  (C8H704)2Ba,  is  extremely  soluble  in 
water,  and  crystallizes  from  dilute  alcohol  in  hydrated  prisms, 
which  decompose  even  at  100°  with  formation  of  barium 
carbonate. 

Methyl  orsellinate,  C8H704(CH3),  is  formed  by  boiling  lecanoric 
acid  (Schunck)  or  erythrin  (Stenhouse)  with  methyl  alcohol,  and 
crystallizes  in  lustrous  needles,  or  flat,  pointed  prisms,  which 

1  Ann.  Chem.  PJiarm  cxxxix.  22.  2  Journ.  Chem.  Soc.  v.  221. 


LECANORIC  ACID.  433 


are  readily  soluble  in  water.  It  dissolves  in  alkalis  and  is 
reprecipitated  by  acids. 

Ethyl  orsellinate,  C8H704(C2H5).  The  formation  of  this  ether, 
which  was  described  by  Heeren  as  pseudoerythrin,  has  been 
frequently  referred  to  in  the  preceding  pages.  It  is  slightly 
soluble  in  cold,  readily  in  hot  water  and  alcohol,  and  crystallizes 
in  needles  or  small  plates,  which  melt  at  132°.  Its  aqueous 
solution  is  precipitated  by  lead  acetate. 

Amyl  orsellinate,  CgHyO^CgHj,),  is  prepared  by  boiling  erythrin 
with  amyl  alcohol.  It  is  scarcely  soluble  in  water,  readily  in 
alcohol  and  ether,  from  which  it  crystallizes  in  vitreous  prisms, 
melting  at  760.1 

Orsellinic  acid  is  decomposed  by  the  action  of  bromine  into 
carbon  dioxide  and  tribromorcinol ;  if,  however,  the  substances 
are  mixed  in  ethereal  solution,  substitution  products  are  formed. 

Dibromorsellinic  acid,  C8H6Br204,  is  slightly  soluble  in  hot 
water,  readily  in  alcohol  and  ether,  and  crystallizes  in  small, 
white  prisms ;  its  alcoholic  solution  is  coloured  a  splendid 
dark  blue  by  ferric  chloride,  and  blood-red  by  bleaching  powder 
(Hesse). 

Phosphorsellinic  acid,  C40H36P4O24.  When  orsellinic  acid  is 
gradually  heated  with  phosphorus  oxychloride  to  90° — 100°,  the 
liquid  becomes  coloured  brown,  violet-green,  and,  finally,  indigo- 
blue.  If  it  be  now  allowed  to  drop  into  ice  water,  phosphorsellinic 
acid  separates  out,  and  may  be  purified  by  repeated  solution  in 
water  and  precipitation  with  hydrochloric  acid  or  common  salt. 
It  is  an  amorphous,  indigo-blue  powder,  which  takes  a  cupreous 
lustre  under  strong  pressure  and  readily  forms  deep  blue  solutions 
in  water  and  alcohol.  The  solution  in  20,000  parts  of  water  has 
the  colour  of  a  concentrated  solution  of  copper  sulphate  and  a 
distinct  violet  colouration  is  visible  when  50,000  parts  of  water 
are  employed.  It  dissolves  in  alkalis,  lime  water  and  baryta 
water  with  a  violet-red  colour ;  the  salts  of  the  heavy  metals 
produce  bluish  violet,  flocculent  precipitates. 

Phosphor sellinanilide,  C40H34(C6H5.NH)2P4O22,  is  formed  by 
boiling  the  acid  with  aniline  and  alcohol ;  it  is  a  dark  violet 
powder,  which  is  insoluble  in  water,  but  forms  a  splendid  violet 

solution  in  alcohol.2 

• 

2232  Lecanoric  acid  or  Diorsellinic  acid,  C16H14O7  -f  H20,  is, 
according  to  He«se,  best  prepared  from  the  JR.  tinctoria  from  Cape 
Verde.  The  lichens  are  extracted  with  ether,  and  the  greenish 

1  Hesse,  Ann.  Chem.  Pharm.  cxxxix.  22.  2  Schiff,  ibid,  ccxxviii.  56. 


434  AKOMATIC  COMPOUNDS. 

white,  crystalline  residue  left  after  the  evaporation  of  the  ether 
dissolved  in  milk  of  lime,  filtered,  precipitated  with  sulphuric 
acid  and  crystallized  from  alcohol.  It  is  scarcely  soluble  in 
cold  water,  but  dissolves  in  2,500  parts  of  boiling  water,  more 
readily  in  alcohol  and  ether,  and  crystallizes  in  needles  or 
prisms,  which  become  anhydrous  at  100°,  melt  at  153°,  and 
simultaneously  decompose  with  evolution  of  carbon  dioxide. 
The  alcoholic  solution  is  coloured  dark  purple-red  by  ferric 
chloride  and  is  not  precipitated  by  lead  acetate ;  copper  acetate, 
however,  produces  a  pale,  apple-green  precipitate  on  standing 
(Schunck).  It  reduces  ammoniacal  silver  solution  on  heating,  and 
is  converted  on  boiling  with  water  into  orsellinic  acid,  and  with 
alcohol  into  its  ether. 

Barium  lecanorate,  (C16H13O7)2Ba,  separates  from  hot  alcohol 
in  small,  star-shaped  aggregates  of  needles. 

Substitution  products  are  formed  by  the  action  of  bromine  on 
an  ethereal  solution : 

Melting- 
point. 

Dibromolecanoric  acid,  C16H12Br207,  small  white  prisms  .  179° 
Tetrabromolecanoric  acid,  C16H10Br4O7,  pale  yellow  prisms  157° 

Both  these  bodies  evolve  carbon  dioxide  on  fusion ;  their 
alcoholic  solutions  are  coloured  purple-red  by  ferric  chloride  and 
blood-red  by  bleaching  powder  (Hesse). 

Erythrin,  2C20H22O10  +  3H2O.  In  order  to  prepare  this  sub- 
stance, 1  part  QtR.fuciformis  is  macerated  for  twenty  minutes  with 
10  parts  of  milk  of  lime  containing  T6  per  cent,  of  lime,  filtered 
and  precipitated  immediately  with  hydrochloric  acid.  The  re- 
sidue is  treated  a  second  time  with  milk  of  lime,  which  is  then 
employed  for  the  extraction  of  a  new  quantity  of  lichen.  The 
precipitate  is  redissolved  in  milk  of  lime,  the  filtrate  treated  with 
carbon  dioxide  and  the  precipitated  mixture  of  calcium  carbonate 
and  erythrin  gently  warmed  with  alcohol;  hot  water  is  then 
added  to  the  solution  until  a  permanent  turbidity  is  produced. 
The  erythrin  separates  on  cooling  in  spherical  crystalline  masses, 
which  become  anhydrous  at  100°  and  melt  at  137°.  It  is 
slightly  soluble  in  cold  water,  with  difficulty  in  ether,  but 
readily  in  alcohol ;  ferric  chloride  added  to  the  alcoholic  solution 
produces  a  purple-violet  colouration,  which  changes  on  further 
addition  to  a  brownish  red  precipitate. 

Picroerythrin,  C12H16O7  +  3H2O,  is  the  first  product  of  the 
decomposition  of  erythrin  by  boiling  water,  alcohols  or  alkalis, 


EVERNIC  ACID.  435 


When  erythrin  is  dissolved  in  milk  of  lime  it  decomposes  in  the 
course  of  a  day  or  two  with  formation  of  picroerythrin,  which  is 
also  obtained  pure  when  erythrin  is  boiled  for  some  hours  with 
amyl  alcohol.  It  crystallizes  in  silky  prisms,  which  readily 
effloresce,  melt  at  158°  and  have  a  slightly  sweet  and  intensely 
bitter  taste.  It  is  exceptionally  soluble  in  hot  water  and  under- 
goes no  change  when  boiled  with  absolute  alcohol.  Ferric 
chloride  produces  a  purple-violet  colouration. 

2233  In  connection  with  these  compounds,  the  following, 
which  are  to  some  extent  homologous  with  them,  may  be 
mentioned  here. 

Evernic  acid,  C17H1607.  According  to  Rochleder  and  Heldt, 
lecanoric  acid  occurs  in  Evernia  Prunastri ;  Stenhouse,  how- 
ever, could  not  detect  it  in  lichens  grown  in  Scotland,  but  found 
in  them  evernic  acid,  together  with  usnic  acid,  C18H1807,  thus 
proving  either  that  the  German  and  Scotch  lichens  contain 
different  compounds,  or,  what  is  much  more  probable,  that  the 
German  chemists  had  not  investigated  the  true  Evernia  Pru- 
nastri,1 a  view  which  is  supported  by  the  fact  that  Hesse,  who 
examined  this  lichen  collected  in  various  parts  of  Germany, 
always  found  evernic  acid  in  it.2 

It  is  almost  insoluble  in  water,  but  dissolves  easily  in  alcohol,  and 
crystallizes  in  spherical  aggregates  of  needles,  which  melt  at  164°. 

Everninic  acid,  C9H1004,  is  formed,  together  with  carbon 
dioxide  and  orcinol,  when  evernic  acid  is  boiled  with  lime  water 
or  baryta  water.  It  is  tolerably  soluble  in  hot  water,  readily  in 
alcohol,  and  crystallizes  in  flat,  lustrous  needles,  resembling 
those  of  benzoic  acid.  It  melts  at  159°,  and  on  further  heating 
emits  a  penetrating  odour  and  yields  a  colourless  sublimate. 
Ferric  chloride  colours  the  aqueous  solution  violet. 

Barlalic  acid,  C19H20O7.  This  substance,  which  stands  in 
the  same  relation  to  homorcinol  (p.  402)  as  evernic  acid  to 
orcinol,  occurs  with  usnic  acid  in  Usnea  larbata.  It  crystallizes 
from  benzene  in  long  plates,  needles,  or  short  prisms,  which 
melt  at  168°,  and  decompose  at  a  higher  temperature  with 
evolution  of  carbon  dioxide  and  formation  of  homorcinol.3 

^Erythrin  or  Homo-ery <thrin ,  C21H24O]0-f-H2O,  was  discovered 
in  a  stunted  specimen  of  E.  fuciformis*  It  crystallizes  in 

1  Ann.  CJiem.  Pharm.  Ixviii.  83  ;  civ.  56.  2  Ibid,  cxvii.  297. 

3  Stenhouse  and  Groves,  Jaurn.  Chcm.  Soc.  1880,  407. 

4  Menschutkin,  Bull.  Soc.  Chim.  [2]  ii.  424  ;  Lamparter,  Ann.  Chem.  Pharm. 
cxxxiv.  234. 


436  AROMATIC  COMPOUNDS. 

concentrically  arranged  needles,  which  are  very  readily  soluble  in 
alcohol.  On  boiling  with  baryta  water  it  is  resolved  into  carbon 
dioxide,  erythrol  and  homorcinol : 

C13H1606  +  2H20  =  C02  +  C4H1004  +  C8H10O2. 

It  is  not  homologous  with  picroerythrin,  but  is  the  anhydride 
of  such  a  compound,  which  would  probably  have  the  following 
constitution  : 

XCO.OV 
(CH3)2C6H(OH)<(  >C4H6(OH)2. 

N .  o  / 

Picrorocellin,  C27H29N3O5,  was  found  along  with  erythrin  by 
Stenhouse  and  Groves  in  a  variety  of  R.  tinctoria  which  pro- 
bably came  from  western  Africa.  It  is  insoluble  in  water, 
tolerably  soluble  in  hot  alcohol,  and  crystallizes  in  long,  lus- 
trous prisms,  which  melt  at  192° — 194°,  and  have  an  intensely 
bitter  taste.  On  oxidation  with  chromic  acid,  benzoic  acid  is 
obtained  together  with  a  liquid  smelling  like  benzaldehyde. 
On  dry  distillation  it  yields  water,  ammonia,  and  xanthorocellin, 
C21H17N2O2,  which  is  also  obtained  by  heating  picrorocellin  with 
dilute  acids,  and  crystallizes  from  alcohol  in  long,  yellow  needles, 
melting  at  1830.1 

2234  Para-orsellinic  acid,  C6H2(CH3)(OH)2C02H  +  H20,  is 
prepared  by  heating  orcinol  with  4  parts  of  ammonium  car- 
bonate and  4  parts  of  water  for  10 — 15  hours  to  the  boiling- 
point  of  amyl  alcohol,2  or  by  passing  carbon  dioxide  over  the 
potassium  compound  of  orcinol  at  250° — 2600.3  It  crystallizes 
from  dilute  alcohol  in  fine,  hard  needles,  which  dissolve  in 
about  660  parts  of  cold  water ;  the  solution  is  coloured  blue  by 
ferric  chloride.  On  heating  the  acid  it  loses  water  at  100°  and 
commenees  to  melt  at  about  150°  with  evolution  of  carbon 
dioxide,  which  is  also  given  off  when  the  acid  is  simply  boiled 
with  water ;  on  dry  distillation  it  decomposes  completely  with 
formation  of  orcinol. 

Barium  para-orsellinate,  (C8H7O4)2Ba  +  6H2O,  crystallizes  in 
four-sided  tablets,  which  are  readily  soluble  in  water. 

Paraphosphorsellinic  acid  is  formed  as  a  chromegreen  powder 
by  heating  para-orsellinic  acid  with  phosphorus  oxychloride 
(p.  433). 

1  Ann.  Chem.  Pharm.  clxxxv.  14. 

*  Brunner  and  Senhofer,  Monatsh.  xiii.  1643. 

8  Schwarz,  Ber.  Deutsch.  Chem.  Oes.  xiii.  1643. 


CRESORSELLINIC  ACID.  437 

Cresordnolcarloxylic  acid,  C6H2(CH3)(OH)2C02H  +  H2O,  is 
formed  when  cresorcinol  is  heated  in  a  small  flask  with  4  parts 
of  potassium  01  sodium  bicarbonate  for  half  an  hour.  It  is 
slightly  soluble  in  cold,  readily  in  hot  water  and  alcohol,  and 
crystallizes  in  very  long,  thin,  lustrous  prisms,  which  lose  their 
water  at  100°  and  melt  at  208°  with  decomposition.  Its  solution 
is  coloured  bluish  violet  by  ferric  chloride  and  is  not  precipitated 
by  lead  acetate.1 

Cresorsellinic  acid,  C6H2(CH3)(OH)2C02H  (1  :2:4:6),  is  pre- 
pared by  fusing  disulphorthotoluic  acid  with  caustic  potash.  It 
is  slightly  soluble  in  cold,  readily  in  hot  water,  and  crystallizes  in 
long,  hard,  vitreous  needles,  which  melt  at  245°.  It  reduces 
ammoniacal  silver  solution  on  heating  and  Fehling's  solution  on 
boiling;  its  aqueous  solution  is  coloured  dark  brown  by  ferric  salts, 
a  ferrous  compound  being  formed.  On  heating  with  sulphuric 
acid  the  liquid  assumes  a  splendid  stable  magenta  colour ;  water 
precipitates  from  it  yellow  flocks,  which  form  an  intense  golden- 
yellow  solution  in  alkalis.  It  therefore  gives  a  similar  reaction 
to  that  which  is  characteristic  of  the  analogous  a-resorcylic  acid 
(p.  358).  When  it  is  heated  to  220°— 225°  with  hydrochloric 
acid,  dark  flocks  separate  out,  which  form  a  reddish  brown 
solution  in  alcohol ;  on  the  addition  of  a  little  alkali,  the  liquid 
takes  a  splendid  dark  green  fluorescence,  which  disappears  when 
an  excess  of  alkali  is  added,  a  deep  purple-red  solution  being 
formed.  Cresorcinol  is  formed  when  the  acid  is  distilled  with 
slaked  lime.2 

Three  carboxylic  acids  are  derived  from  cresorcinol : 

C02H  C02H  C02H 

OH/\OH 

OH 

The  last  of  these  expresses  the  constitution  of  cresorsellinic 
acid,  which  is  a  derivative  of  orthotoluic  acid.  The  second 
probably  represents  that  of  cresorcinolcarboxylic  acid,  since  the 
readiness  with  which  it  is  formed  supports  the  conclusion  that 
the  carboxyl  takes  up  the  same  position  in  the  nucleus  in  the 
case  of  cresorcinol  as  it  does  in  the  analogous  formation  of 
/8-resorcylic  acid  from  resorcinol  (p.  359). 


1  Kostanccki,  Ber.  DeutscTi.  CJiem.  Gcs.  xviii.  3202. 

2  Jacobsen  and  Wierss,  ibid.  xvi.  1956. 


259 


438  AROMATIC  COMPOUNDS. 

The  constitution  of  para-orsellinic  acid,  and  therefore  that  of 
orsellinic  acid,  follows  from  these  considerations  (Kostanecki) : 

Orsellinic  acid.  Para-orsellinic  acid. 

CO2H  CO2H 

OH 


1 

CH3  OH. 

2235  Homohydroxysalicylic  acid,  C6H2(CH3)(OH)2C02H,  is 
prepared  by  heating  40  grms.  of  toluquinol  for  thirty-six  hours 
in  a  bath  of  oil  of  turpentine  with  130  grms.  of  potassium 
bicarbonate,  110  ccs.  of  water,  and  40  ccs.  of  a  saturated 
solution  of  potassium  sulphite.  It  dissolves  in  1,366  parts  of 
water  at  8°,  more  readily  in  hot  water,  and  crystallizes  from 
dilute  alcohol  in  microscopic,  acute  rhombic  plates,  while,  when 
prepared  from  the  ammoniacal  salt  by  precipitation  with  hydro- 
chloric acid,  it  separates  as  a  crystalline  powder  containing  half 
a  molecule  of  water.  Ferric  chloride  produces  an  azure-blue 
colouration,  which  passes  into  a  beautiful  green  on  standing 
or  on  the  addition  of  an  excess  of  the  chloride ;  it  reduces 
Fehling's  solution  on  warming,  but  a  neutral  silver  solution  in 
the  cold.  It  is  decomposed  at  210° — 220°  into  carbon  dioxide 
and  toluquinol.1 

Barium  homohydroxysalicylate,  (C8H704)2Ba  +  2H2O,  forms 
fine  prismatic  needles,  readily  soluble  in  water. 

Creosolcarboxylicacid,  C6H2(CH3)(OCH3)(OH)CO2H  (1:3:4:5). 
According  to  the  researches  of  Kostanecki,  only  those  phenols 
which  contain  hydroxyl  groups  in  the  meta-position  are  con- 
verted into  carboxylic  acids  by  boiling  with  the  alkali  bicar- 
bonates,  and  as  creosol  does  not  belong  to  this  class  of  bodies, 
the  corresponding  acid  is  prepared  by  adding  sodium,  warming 
gently  and  passing  in  a  current  of  carbon  dioxide. 

Creosolcarboxylic  acid  crystallizes  from  a  mixture  of  chloroform 
and  benzene  in  concentrically  arranged  needles,  which  melt  at 
180° — 182°  and  sublime  when  carefully  heated.  It  is  readily 
soluble  in  alcohol,  ether  and  chloroform,  but  only  slightly  in 
water  and  scarcely  at  all  in  benzene  and  petroleum  ether ;  its 
solution  is  coloured  deep  blue  by  ferric  chloride.  The  barium 
salt  crystallizes  in  small,  anhydrous  needles,  which  are  only 
slightly  soluble  in  water. 

1  Brunner,  Monatsh.  Chem.  ii.  458. 


XYLYLENE  ALCOHOLS.  439 

Methyl  creosolcarloxylate,  C6H4(CH3)(OCH3)(OH)C02.CH3, 
forms  small,  rhombic  prisms,  melts  at  92°  and  gives  a  bluish 
green  colouration  with  ferric  chloride.1 


,CH2.OH 


XYLYLENE  ALCOHOLS,  C6H4< 


2236  Orthoxylylene  alcohol  was  first  prepared  by  the  action  of 
sodium  amalgam  on  a  boiling  solution  of  phthalyl  chloride, 
C6H4.C2O2C12  (p.  458),  in  glacial  acetic  acid,  and  named  phthal- 
alcohol.2  It  is  also  obtained  by  boiling  its  bromide  with  a  solution 
of  sodium  carbonate  3  or  potassium  carbonate.4  It  is  tolerably 
soluble  in  water,  readily  in  alcohol,  and  crystallizes  in  rhombic 
tablets,  which  have  a  bitter  taste  and  melt  at  64*5°.  Concentrated 
sulphuric  acid  imparts  to  them  a  red  colour  and  then  converts  them 
into  a  resinous  mass.  Potassium  permanganate  or  chromic  acid 
oxidize  it  to  phthalic  acid,  while  it  is  reduced  to  orthoxylene  by 
heating  with  hydriodic  acid  and  amorphous  phosphorus. 

Orthoxylylene  ethyl  ether,  C6H4(CH2OC2H5)2,  is  obtained  by 
boiling  the  bromide  with  alcoholic  potash,  and  is  a  very  pleasant- 
smelling,  oily  liquid,  which  boils  at  247° — 249°  (Leser). 

Orthoxylylene  chloride,  C6H4(CH2C1)2,  is  formed  when  ten 
ccs.  of  orthoxylene  are  heated  to  190°  with  35  grms.  of  phos- 
phorus pentachloride,5  as  well  as  by  heating  the  alcohol  with 
hydrochloric  acid,  and  separates  from  ether  in  crystals,  which 
melt  at  54*8°  and  readily  sublime.  Its  vapour  attacks  the  eyes 
with  great  violence. 

Raymann,  by  the  action  of  chlorine  on  boiling  orthoxylene, 
obtained  an  isomeric  substance,  which  crystallizes  in  tablets  and 
melts  at  1030.6  These  properties  correspond  with  those  of 
paraxylylene  chloride,  and  the  hydrocarbon  employed  by  Ray- 
mann must  have  contained  paraxylene,  which  is  much  more  readily 
attacked  by  chlorine  and  bromine  than  its  isomerides.  This 
property  can  be  made  use  of  to  detect  even  traces  of  paraxylene 
in  the  presence  of  the  ortho-  and  meta-  compounds ;  the 

1  Wende,  Ber.  Deutsch.  Chem.  Ges.  xix.  2324.  2  Hessert,  ibid.  xii.  642. 

3  Baeyer  and  Perkin,  xvii.  122. 

4  Colson,  Ann.  Chim.  Phys.  [6]  vi.  104. 

6  Colson  and  Gautier,  Bull.  Soc.  Chim.  xlv,  6  :  Colson,  Ann.  Chim.  Phys.  [6] 
vi.  108. 

6  Bull.  Soc.  Chim.  xxvi.  553. 


440  AROMATIC  COMPOUNDS. 

mixture  is  treated  at  the  boiling  point  with  sufficient  bromine 
to  form  the  monobromo-derivatives  ;  any  paraxylene  present  is 
converted  into  paraxylylene  bromide,  which  separates  out  on 
cooling.1 

Orthoxylylene  bromide,  C6H4(CH2Br)2  is  obtained  when  or- 
thoxylene  is  heated  with  the  calculated  quantity  of  bromine  to 
150°  —  155°,  or  when  the  latter  is  allowed  to  drop  into  the  boil- 
ing hydrocarbon,  the  temperature  being  gradually  raised  to  180°. 
It  is  also  formed  when  orthoxylene  is  treated  with  bromine  in  the 
sunlight,2  and  crystallizes  from  chloroform  in  splendid,  rhombic 
pyramids,  which  melt  at  94'9°,  and  dissolve  in  5  parts  of 
ether. 

Orthoxylylene  iodide,  C6H4(CH2I)2,  is  prepared  by  heating  the 
alcohol  with  phosphorus  and  hydriodic  acid,  and  crystallizes 
from  ether  in  splendid,  well-formed  yellowish  prisms,  melting  at 
109°—  110°.3 

Orthoxylylene  acetate,  C6H4(CH2O.CO.CH3)2,  is  formed  by  the 
action  of  acetyl  chloride  on  the  alcohol  ;  it  is  a  crystalline  mass, 
which  melts  at  37°  and  boils  without  decomposition. 


Orthoxylylene  sulphide,  C6H4\  ")S,  is  obtained  by  heating 

X/ 


the  bromide  with  an  alcoholic  solution  of  potassium  sulphide, 
and  is  a  colourless  liquid  which  smells  like  mercaptan  and 
solidifies  in  large  crystals  at  about  0°  (Leser). 

Diphenylorthoxylylenediamine,  C6H4(CH2.NH.C6H5)2,  is  pre- 
pared by  the  action  of  aniline  on  the  bromide.  It  crystallizes 
from  alcohol  in  small  plates,  melting  at  172°,  and  dissolves  in 
concentrated  hydrochloric  acid,  but  is  reprecipitated  by  water. 

Metaxylylene  alcohol,  C6H4(CH2.OH)2.  This  compound,  which 
is  also  known  as  isophthalalcohol,  is  prepared  by  heating  the 
bromide  with  a  solution  of  carbonate  of  potassium.  It  is  readily 
soluble  in  water  and  separates  from  ether  as  an  oily  liquid, 
which  solidifies  to  microscopic,  twinned  crystals,  melting  at 
46°—  47°.*  ' 

Metaxylylene  ethyl  ether  is  obtained  by  heating  the  bromide 
with  alcoholic  potash,  and  is  an  oily  liquid,  which  boils  at 
247°  —  249°,  and  is  oxidized  by  chromic  acid  to  isophthalic  acid.5 

1  Radziszewski  and  Wispek,  Ber.  Dcutsch.  Chem.  Ges.  xviii.  1279. 

2  Schramm,  ibid,  xviii.  1272. 

3  Leser,  ibid.  xvii.  1824. 

4  Colson,  Ann.  Chim.  Phys.  [6]  vi.  109. 

5  W.  H.  Perkin,  jun.,  Private  communication. 


METAXYLYLENE  CHLORIDE.  441 

Metaxylykne  chloride,  C6H4(CH2C1)2,  is  prepared  by  heating 
the  alcohol  with  hydrochloric  acid  (Colson);  it  is  also  formed 
when  metaxylene  is  heated  with  phosphorus  pentachloride, 
the  yield  being,  however,  very  poor  (Colson  and  Gautier).  It 
crystallizes  in  pointed  prisms,  melts  at  34°  and  boils  at  250° — 
2550.1 

Metaxylylene  bromide,  C6H4(CH2Br)2,  forms  long,  prismatic 
needles,  melting  at  77°,  and  is  obtained  by  heating  metaxylene 
with  bromine  (Colson,  Radziszewski  and  Wispek),  as  well  as 
by  bringing  these  two  substances  together  in  the  sunlight 
(Schramm). 

Paraxylylene  alcohol,  C6H4(CH2.OH)2,  was  prepared  by  Gri- 
maux  by  heating  the  chloride  or  bromide  with  30  parts 
of  water  to  170° — 180°,  and  was  named  tolly lene  glycol.2  It 
crystallizes  in  lustrous  needles,  which  melt  at  112° — 113°,  are 
readily  soluble  in  water,  alcohol  and  ether,  and  are  converted  by 
oxidation  into  terephthalic  acid. 

Paraxylylene  mono-ethyl  ether,  C6H4(CH2.OH)CH2.O.C2H5,  is 
formed  when  the  chloride  is  heated  with  alcoholic  potash ;  it  is 
a  pleasant-smelling  liquid  which  boils  at  250° — 2520.3 

Paraxylylene  chloride,  C6H4(CH2C1)2,  is  prepared  by  the  action 
of  chlorine  on  boiling  paraxylene,4  or  by  heating  the  alcohol 
with  hydrochloric  acid.  It  may  also  be  obtained  in  a  similar 
manner  to  the  ortho-compound  by  heating  paraxylene  with 
phosphorus  pentachloride  (Colson  and  Gautier).  It  crystallizes 

)m  alcohol  in  pointed,  rhombic  tablets,  melts  at  100°  and 
>ils  with  decomposition  at  240° — 250°. 

Paraxylylene  bromide,  C6H4(CH2Br)2,  is  obtained  by  passing 
bromine  vapour  into  paraxylene  or  by  heating  the  alcohol  with 
hydrobromic  acid ;  it  boils  at  240° — 250°,  and  crystallizes  from 
chloroform  in  plates,  which  melt  at  143'5°,5  and  dissolve  in  about 
>0  parts  of  ether. 

Paraxylylene  iodide,  C6H4(CH2I)2,  is  prepared  by  heating  the 
ilcohol  with  hydriodic  acid  ;  it  forms  fine  needles,  which  melt 
it  170°,  and  rapidly  become  coloured  yellow  in  the  air. 

Paraxylylene  acetate,  C6H4(CH2.O.CO.CH3)2,  is  formed  when 
the  chloride  is  heated  to  150°  with  an  alcoholic  solution  of 
sodium  acetate.  It  is  readily  soluble  in  alcohol  and  ether,  and 

1  Bull.  Soc.  Chim.  xliii.  6.  2  Ann.  Chem.  Pharm.  civ.  338. 

3  Grimaux,  Butt.  Soc.  Chim.  xvi.  193. 

4  Grimaux,  Zcitschr.  Chem.  1867,  381. 

6  Radziszewski  and  Wispek,  Ber.  Dcutsch.  Chem.  Oes.  xviii.  1280  ;  Low,  ibid, 
xviii.  2072. 


442  AROMATIC  COMPOUNDS. 

crystallizes  from  the  latter  in  hard,  lustrous  plates,  which  have  a 
pungent,  camphor-like  taste,  and  melt  at  47°. 

Paraxylylene  monobenzoate,  C6H4.(CH2.OCO.C6H5)CH2.OH,  is 
obtained  by  heating  the  chloride  with  an  alcoholic  solution  of 
sodium  benzoate,  and  crystallizes  in  long,  thin  needles,  melting  at 
73°— 74°. 


HYDROXYMETHYLBENZOIC  ACIDS, 
C0H 


2237  These  compounds  are  isomeric  with  the  hydroxytoluic 
acids,  from  which  they  differ  in  being  alcohols  while  the  latter 
are  phenols. 

Parahydroxymeihylbenzoic  acid  was  prepared  by  Dittmar  and 
Kekule,  who  named  it  oxymethylphenylformic  acid,  by  heating 
paratoluic  acid  with  bromine  at  160°  —  170°,  and  boiling  the 
product  with  baryta  water.  It  crystallizes  in  white  plates  or 
flat  needles,  which  are  more  readily  soluble  in  water  than  para- 
toluic acid,  melt  a  few  degrees  higher  and  sublime  in  feathery 
needles.1 

Orthohydroxymethylbenzoic  acid  was  first  prepared  by  Hessert, 
who  named  it  "  Benzolorthoalcoholsaure"  by  the  action  of  alkalis 
on  phthalide,  which  is  its  anhydride.  Acids  precipitate  it  as  a 
fine  powder,  which  is  slightly  soluble  in  cold  water,  readily  in 
alcohol,  has  a  strongly  acid  reaction,  and  melts  at  118°,  being 
thus  converted  into  the  anhydride,  which  is  also  formed  when 
the  acid  is  simply  boiled  with  water. 

Silver  orthohydroxymethylbenzoate,  C8H7O3Ag,  crystallizes  from 
water  in  small  octohedra. 

Phthalide,  C8H6O2,  was  obtained  by  Kolbe  and  Wischin,  who 
prepared  it  by  the  action  of  zinc  and  hydrochloric  acid  on 
phthalyl  chloride,  C8H402C12,  and  named  it  pJithalaldehyde, 
C6H4(COH)2.2  It  is  also  formed  by  the  action  of  phosphorus 
and  hydriodic  acid  on  the  chloride,3  and  when  orthoxylidene 
chloride  is  boiled  with  water  and  lead  nitrate.4  Hessert  has  proved 

1  Ann.  Chem.  Pharm.  clxii.  337. 

2  Zeitschr.  Chem.  1866,  315. 

3  Baeyer,  Ber.  Deutsch.  Chem.  Ges.  x.  123. 

4  Raymann,  Bull.  Soc.  Chim.  x.  1180. 


PHTHALIDE.  443 


that  it  is  not  the  aldehyde  of  phthalic  acid  but  the  anhydride  or 
lactone  of  the  preceding  compound.1  Its  formation  was  explained 
by  the  following  reactions  : 

/COC1  /CH2.OH 

C6H4<  +  4H  =  C6H4<  +  HC1. 

\COC1  \COC1 

/CH2.OH  XCH2X 

C6H4<  =  C6H/          \0  +  HCL 

\COC1  \CO/ 

It  has  since  been  shown  that  phthalyl  chloride  has  not 
the  constitution  assumed  above  (p.  460),  and  the  formation  of 
phthalide  is  now  represented  much  more  simply  : 


C6H4<  0  +  4H  =  C6H  >0  +  2HC1. 

\CO/  \CO/ 

This  is  confirmed  by  the  observation  of  Hjelt,who  found  that  it 
is  also  obtained  when  bromine  is  passed  into  orthotoluic  acid  heate'd 
to  140°  ;  the  brominated  acid  which  is  first  formed  being  decom- 
posed as  follows  :  2 


C6H4  =C6H4  0  +  HBr. 

\CO.OH  \COX 

It  crystallizes  from  boiling  water  in  needles  which  smell  like 
cinnamon,  melts  at  73°  and  boils  at  290°  (Grabe).  It  does  not 
combine  with  hydroxylamine,3  gives  no  compounds  with  the  acid 
sulphites  of  the  alkalis  and  does  not  reduce  ammoniacal  silver 
solution  (Hessert).  It  is  oxidized  to  phthalic  acid  by  alkaline 
permanganate,  while  it  is  reduced  to  orthotoluic  acid  on  heating 
with  phosphorus  and  hydriodic  acid,  and  to  orthoxylene  together 
with  a  little  toluene  by  heated  zinc  dust. 

Monobromoplithalide  is  formed  by  the  action  of  bromine  vapour 
on  heated  phthalide  ;  it  crystallizes  in  plates,  melting  at  86°,  and 
is  converted  into  phthalaldehydic  acid  (p.  447)  when  heated  with 
water  ;  it  has,  therefore,  the  following  constitution  :  4 

/CHBr 
C6H4<    >  O. 
\GO 

1  Ber.  Deutsch.  Chem.  Ges.  x.  1445  ;  xi.  237.  2  Ibid.  xix.  412. 

3  Lach,  ibid.  xvi.  1782.  4  Racine,  ibid.  xix.  778, 


444  AROMATIC  COMPOUNDS. 

Dibromoplitlialide,  C8H4Br2O2,  is  obtained,  together  with 
dibromonaphthoquinone,  by  the  oxidation  of  a-dibromo- 
naphthalene  with  chromic  acid,  and  crystallizes  from  boiling 
alcohol  in  hard,  white  prisms,  which  sublime  in  needles  and  melt 
at  187'5° ;  it  does  not  reduce  ammoniacai  silver  solution  and  only 
dissolves  slowly  in  boiling  caustic  soda  solution.1  It  has  the 
following  constitution : 

CBr 


HC        C— CH2 

I         II       >0. 
HC        C—  CO 

CBr 

Guareschi  obtained  dichlorophthalide  in  a  similar  manner 
from  dichloronaphthalene ;  it  resembles  the  bromine  compound, 
and  melts  at  1630.2 

Hydrophthalide,  C8H8O2,  is  formed  together  with  phthalyl- 
pinacone,  C1CH18O4,  by  the  action  of  sodium  amalgam  on  an 
acid  solution  of  phthalide,  and  is  a  syrupy  mass,  extremely 
soluble  in  all  solvents  ;  it  probably  has  the  following  constitution 
(Hessert) : 

XCH2 

C6H4<  >  O. 
XCH.OH 

Phthalimidine,  C8H7NO,  is  obtained  by  heating  phthalide 
with  zinc  ammonium  chloride,  or  by  treating  it  at  its  boiling- 
point  with  ammonia : 


/C 


O  /C=:NH 

O  +  NH3  =  C6H4<    >  O      +  H20. 
\CH0 


It  may  be  more  simply  prepared  by  the  action  of  tin  and 
hydrochloric  acid  on  phthalimide,  C6H4(C2O2)NH.  It  is  readily 
soluble  in  alcohol  and  hot  water,  crystallizes  in  prisms  or 
needles,  melts  at  150°  and  boils  at  337°.  When  sodium 
nitrite  is  added  to  its  solution  in  hydrochloric  acid,  yellow 
needles  of  nitrosophthalimidine separate  out;  they  melt  at  156°, 

1  Guareschi,  Ann.  Chem.  Pharm.  ccxxii.  282. 

2  Ber.  Deutsch.  Chem.  Ges.  xix.  1155. 


METHYLPHTHALIMIDINE.  445 

and  are  rapidly  converted  into  orthohydroxymethylbenzoic  acid 
by  the  action  of  aqueous  caustic  soda  : 


/C02Na 

>0  +  NaOH  =  C6H4<(  +  N2. 

\CH2.OH 

Hydrochloric  acid  precipitates  either  the  free  acid  or  phthalide 
from  this  solution  according  to  the  temperature,  and  the  latter 
substance  is  in  fact  most  conveniently  prepared  in  this  way  from 
phthalimide,  which  can  itself  be  readily  obtained  from  phthalic 
acid.1 

•  Methylphthcdimidine,  C8H6O(NCH3),  is  formed  by  the  action 
of  tin  and  hydrochloric  acid  on  methylphthalimide,  and  is  readily 
soluble  in  water,  alcohol  and  ether,  from  which  it  crystallizes  in 
large  tablets,  melting  at  120°;  it  boils  without  decomposition  at 
about  3000.2 

PhenylphtJialimidine  or  Phthalide-anil  is  prepared  by  heating 
phthalide  to  200°—  220°  with  aniline  : 

CO  '  /C=N.CflH6 

6H5  =  C6H4      >0         +H2O. 


It  crystallizes  from  alcohol  in  silvery  plates,  melting  at   160° 
(Hessert). 

Phthalidehydrazide,  C14H12lSr2O,  is  formed  by  heating  phthalide 
with  phenylhydrazine  for  some  time  : 


CH2 

>O  +  H20. 


CO  C=N2H.C6H5 

It   crystallizes   from   hot   water   or   alcohol   in   needles,  which 
possess  a  silver  lustre,  and  melt  at  1650.3 

Paranitropkthalide,  C8H5(N02)02,  is  prepared  by  dissolving 
20  grms.  of  phthalide  in  200  grms.  of  sulphuric  acid,  and 
running  in  a  solution  of  rather  more  than  the  calculated 
quantity  of  potassium  nitrate  in  80  grms.  of  sulphuric  acid,  the 
solution  being  well  cooled  during  the  operation.  It  forms  long, 
colourless  needles,  which  melt  at  141°,  and  are  almost  insoluble  in 
cold  water,  but  dissolve  slightly  on  boiling,  more  readily  in  alcohol, 

1  Grabe,  Bcr.  Deutsch.  Chem.  Ges.  xvii.  2598  ;  xviii.  1408. 

2  Grabe  and  Pictet,  ibid,  xviii.  1173. 

3  V.  Meyer  and  Miinchmeyer,  ibid.  xix.  1706  and  2132. 


446  AROMATIC  COMPOUNDS. 

and  readily  in  benzene.  Alcoholic  potash  produces  a  charac- 
teristic violet  colouration,  while  aqueous  potash  forms  a  yellow 
solution.  Dilute  sulphuric  acid  precipitates  paranitrohydroxy- 
methylbenzoic  acid,  C6H3(NO2)(CH2.OH)C02H,  from  the  cool 
solution.  This  body  crystallizes  in  microscopic  needles  united 
in  stellate  forms,  and  is  extremely  soluble  in  ether,  readily  in 
alcohol  and  hot  water.  It  melts  at  129°,  and  decomposes  at  a 
higher  temperature  into  water  and  nitrophthalide. 

Paramidophthalide,  C8H5(NH2)O2,  is  obtained  by  the  reduc- 
tion of  the  preceding  compound,  and  is  almost  insoluble  in 
water,  but  dissolves  slightly  in  alcohol,  and  more  readily  in 
chloroform,  from  which  it  crystallizes  in  short  prisms,  melting 
at  178°.  Its  hydrochloride  forms  needles  which  are  readily 
soluble  in  water.  It  also  dissolves  in  alkalis,  salts  of  para- 
amidohydroxymethylbenzoic  acid  being  formed.  The  free  acid  has 
not  yet  been  prepared. 

When  paranitrophthalide  is  heated  with  hydriodic  acid  and 
phosphorus,  7-amido-orthotoluic  acid  is  formed.1 

Orthonitrophthalide  was  prepared  by  Beilstein  and  Kurbatow, 
together  with  the  corresponding  nitrophthalic  acid,  by  oxidizing 
a-nitronaphthalene  with  a  solution  of  chromium  trioxide  in 
acetic  acid.  They  mention  that  the  substance  obtained  has 
the  formula  of  nitrophthalaldehyde,  but  must  possess  a  different 
constitution,  because  it  is  only  attacked  with  difficulty  by  the 
oxidizing  mixture  just  named.2  Its  properties  prove  that  it  is 
actually  Orthonitrophthalide.3 

It  crystallizes  in  small  plates,  melting  at  136°,  is  much  more 
readily  soluble  in  alcohol  and  chloroform  than  the  para-com- 
pound, and  forms  a  yellow  solution  in  alkalis.  On  heating  in  a 
sealed  tube  with  dilute  hydrochloric  acid,  it  is  smoothly  con- 
verted into  v-nitrophthalic  acid  (Honig). 

1  Honig,  Bcr.  Deutsch.  Chem.  Ges.  xviii.  3447. 

2  Ann.  Chem.  Pharm.  ccii.  217. 

3  Guareschi,  ibid,  ccxxii.  283  ;  Honig,  loc.  cit. 


PHTHALALDEHYDE.  447 


ALDEHYDES,  C6H4(CHO)2,  AND  ALDEHYDO- 
ACIDS,  C6H4(COH)(COOH). 

2238  Phthalaldehyde.  When  orthoxylejie  is  submitted  at  the 
boiling-point  to  the  continued  action  of  chlorine,  or  is  heated  to 
195°  with  eight  parts  of  phosphorus  pentachloride,  orthoxylidene 
tetrachloride,  C6H4(CHC12)2,  is  formed  ;  it  crystallizes  from  ether 
in  large  asymmetric  prisms,  melts  at  89°  and  boils  at  273°  —  274°. 
On  heating  with  water  it  is  converted  into  phthalaldehyde,  which 
is  also  formed  by  the  oxidation  of  phthal  alcohol,  and  is  an  oily 
liquid,  which  has  not  yet  been  prepared  pure  since  it  so  readily 
passes  into  the  isomeric  phthalide  (Hjelt).  According  to  Colson 
and  Gautier,  phthalaldehyde  is  a  yellow  crystalline  substance 
melting  at  52°.  Ammonia  produces  a  deep  blue  or  yellow 
colouration,  followed  by  a  brown  precipitate.1 

Phthalaldehydic  acid  is  prepared  by  heating  monobromo- 
phthalide  with  water  :  2 


XCHO 

=  C6H4<  H-HBr. 

-  CO   <  \CO.OH 

It  may  also  be  obtained  by  heating  orthoxylene  to  200  with 
12*  5  parts  of  phosphorus  pentachloride  and  boiling  the  product, 
xylidenyl  pentachloride,  C6H4(CHC12)CC13,  with  water  (Colson 
and  Gautier).  It  forms  lemon-yellow  crystals,  which  melt  at  98° 
to  100°,  and  are  readily  soluble  in  water.  Its  phenylhydrazine 
compound  crystallizes  in  fine,  yellow  needles. 

Isophthalaldehyde  is  prepared  in  a  similar  manner  from  meta- 
xylidene  tetrachloride,  C6H4(CHC12)2,  which  is  a  liquid  boiling 
at  273°.  It  is  an  oily  liquid  which,  as  well  as  its  solution  in 
water,  gives  a  green  colouration  with  ammonia,  f  llowed  by  a 
brown  precipitate  (Colson  and  Gautier). 

Terephthalaldehyde,  C6H4(CHO)2,  was  obtained  by  Grimaux 
from  paraxylylene  chloride,  C6H4(CH2C1)2,  by  boiling  with  lead 
nitrate  and  water,3  while  Low  prepared  it  by  the  same  method 
from  paraxylylene  bromide.4 

1  Hjelt,  Bcr.  Dcutsch.  Chcm.  Ges.  xviii.  2879  ;  xix.  411  ;  Colson  and  Gautier, 
Bull.  Soc.  Chim.  xlv.  6  and  506. 

2  Racine,  Bcr.  Dcutsch.  Chcm.  Ges.  xix.  778. 

3  Jahrsber.  Chcm.  1876,  490  ;  Colson  and  Gautier,  loc.  cit. 

4  Ann.  Chcm.  Pharm.  ccxxxi.  361. 


448  AROMATIC  COMPOUNDS. 

It  is  also  formed  when  paraxylene  is  heated  to  190°  with 
eight  parts  of  phosphorus  pentachloride,  and  the  paraxylidene 
tctrachloride  which  is  thus  formed  boiled  with  water  for 
some  time.  The  latter  forms  well-developed  crystals,  melting 
at  93°. 

Terephthalaldehyde  is  only  very  slightly  soluble  in  cold  ether, 
but  readily  in  alcohol  and  tolerably  freely  in  hot  water,  from 
which  it  crystallizes  in  fine  needles,  melting  at  116°.  It  forms 
a  readily  soluble  compound  with  acid  sodium  sulphite.  Con- 
centrated caustic  soda  solution  decomposes  it  with  formation  of 
parahydroxymethylbenzoic  acid,  paraxylylene  alcohol  and  tere- 
phthalic  acid  : 

/CHO  /CH2.OH 

C6H4<;  +H20  =  C6H4< 

\CHO  \CO.OH. 

/CH2.OH  XCH2.OH  CO.OH 

2C6H4<  = 

\CO.OH 


4  6 

\CH.OH  \CO.OH. 


Terephthalaldehyde  is  also  obtained  when  paraxylylene  bro- 
mide is  dissolved  in  cold,  concentrated  nitric  acid.  The  com- 
pound C24H20Br204  is  simultaneously  formed  ;  it  is  insoluble  in 
water,  but  dissolves  readily  in  -ether,  from  which  it  crystallizes  in 
stunted  needles,  which  melt  at  80°  and  are  converted  into  tere- 
phthalaldehyde,  paraxylylene  alcohol  and  hydrobromic  acid,  by 
heating  with  water  : 

/CHO 
C6H4< 

\CHBr.O.CH2X 

>C6H4  +  2H20  = 
/CHBr.O.CH/ 
C6H4< 

\CHO 

/CHO       HO.CH2X 

C6H4  +  2HBr. 


\CHO       HO.CH 

It  is  noteworthy  that  concentrated  nitric  acid  exerts  an 
oxidizing  action  upon  paraxylylene  bromide,  and  does  not  effect 
nitration  as  in  the  case  of  benzyl  chloride.1 

Xylylidenediamine,    C8H8N2,   is    deposited    in    very    brittle, 

1  Low,  Ber.  Deutsch.  Chem.  Ges.  xviii.  20/2. 


HYDROBENZAMIDE  TRIALDEHYDE.  449 

vitreous  crystals  when  an  alcoholic  solution  of  terephthalaldehyde 
is  saturated  with  ammonia  and  allowed  to  stand : 

/CHO  /CH=NH 

C6H4<  +  2NH3  =  C6H4<  _  +  2H20. 


It  is  also  formed  when  dry  ammonia  is  passed  over  the 
aldehyde,  but  is  decomposed  again  by  acids,  or  even  on  boiling 
with  water,  into  ammonia  and  the  aldehyde. 

Hydrobenzamide  trialdehyde,  N2(CH.C6H4.CHO)3$  is  formed 
by  the  action  of  aqueous  ammonia  on  terephthalaldehyde,  as  a 
white  powder  consisting  of  matted  microscopic  needles,  which  is 
insoluble  in  water  and  alcohol  and  is  dissolved  by  acids,  the 
aldehyde  being  set  free.1 

Nitroterephthalaldehyde,  C6H3(N02)(CHO)2.  In  order  to  pre- 
pare this  substance,  a  solution  of  the  aldehyde  heated  to  150°  is 
treated  with  an  equal  quantity  of  potassium  nitrate  dissolved  in 
sulphuric  acid,  kept  at  a  temperature  of  110° — 115°  for  10 — 15 
minutes,  poured  into  water  and  then  extracted  with  ether.  It 
is  very  readily  soluble  in  alcohol,  with  greater  difficulty  in  hot 
water  and  ether,  crystallizing  from  the  latter  in  rhombohedra, 
which  melt  at  86°  and  sublime  in  large  needles.  A  blue  indigo 
derivative  is  formed  when  it  is  heated  with  caustic  soda  and 
acetone  (p.  146)  (Low). 

Terephthalaldehydic  acid,  C6H4(CHO)C02H,  is  formed,  together 
with  terephthalic  acid,  by  the  oxidation  of  the  aldehyde  with 
chromic  acid  solution.  It  is  only  slightly  soluble  in  ether  and 
chloroform,  and  still  less  readily  in  hot  water,  from  which  it 
crystallizes  in  needles,  which  melt  at  246°  .and  sublime  in  well- 
formed  needles.  It  forms  a  barium  salt  which  is  readily  soluble 
in  water,  as  well  as  a  scarcely  soluble  silver  salt,  and  only 
reduces  ammoniacal  silver  solution  after  continued  boiling. 

The  ethyl  ether,  C6H4(CHO)CO2.C2H5,  forms  groups  of  pointed 
needles,  easily  reduces  ammoniacal  silver  solution  on  heating, 
and  gives  all  the  reactions  of  benzaldehyde  (Low). 

Hydrdbenzamidctricarloxylic  acid,  N2(CH.C6H4.CO2H)3  is  not 
formed  by  the  action  of  ammonia  on  the  aldehydo-acid,  but  by 
the  oxidation  of  the  trialdehyde  with  potassium  permanganate. 
It  crystallizes  in  nacreous,  rhombohedral  tablets  (Oppenheimer). 

NitrotcrcpUhalaldehydic  acid,  C6H3(NO2)(CHO)C02H(2 : 1 :  4, 
1  Oppenheimer,  Bcr.  Dcutsch.  Chem.  Ges.  xix.  574. 


450  AROMATIC  COMPOUNDS. 

is  prepared  in  a  similar  manner  to  nitrophthal aldehyde.  It  is 
readily  soluble  in  hot  water,  and  crystallizes  from  it  in  large, 
four-sided  needles,  which  melt  at  160°.  On  heating  with  caustic 
soda  solution  and  acetone  it  is  converted  into  indigocarboxylic 
acid,  C16H8N202(CO2H)2,  a  reaction  which  proves  that  the 
nitroxylyl-group  stands  in  the  ortho-position  with  respect  to 
the  aldehyde  group. 

In  its  preparation  a  small  quantity  of  the  isomeric  acid 
(NO2:COH:C02H=:3:1:4),  which  melts  at  184°,  is  also 
formed  (Low). 


/C02H 
THE  PHTHALIC   ACIDS,  C6H4< 

XC02H. 

2239  In  the  year  1836,  Laurent  prepared  naphthalic  acid  (acide 
naphtalique),  C10H6O5,  by  boiling  naphthalene  tetrachloride, 
C10H8C14,  with  nitric  acid,1  and  Marignac,  who  was  subsequently 
confirmed  by  Laurent,  proposed  for  it  the  formula  C8H6O4.  The 
latter  chemist  found  that  it  is  also  obtained,  together  with  other 
products,  by  boiling  naphthalene  with  nitric  acid,  oxalic  acid 
being  always  simultaneously  formed.2  Since  it  no  longer 
belongs  to  the  naphthalene  series,  he  named  it  phthalic  acid 
(acide  phtalique)?  It  decomposes  on  distillation  with  lime,  as 
was  shown  by  Marignac,  into  carbon  dioxide  and  benzene.4 

During  his  investigation  of  the  colouring  matter  of  madder 
root,  Schunck  found  that  alizarin  is  converted  by  oxidation  into 
alizaric  acid,  CUH10O7,5  which,  according  to  Gerhardt,6  con- 
firmed by  Strecker  and  Wolff,7  is  identical  with  phthalic  acid. 
The  naphthesic  acid  (acide  naphtesique),  C10HCO4,  which  Laurent 
had  obtained  by  the  action  of  potassium  dichromate  and 
sulphuric  acid  on  naphthalene,8  was  also  recognized  as  phthalic 
acid  by  Scheibler  9  and  F.  Lossen,  the  latter  of  whom  found  that 
it  is  also  formed  by  the  action  of  potassium  permanganate  on 
naphthalene.10  An  isomeric  substance  was  prepared  by  Cailletet 

1  Ann.  CMm.  Phys.  Ixi.  114  ;  Ann.  Chem.  Pharm.  xix.  38. 

2  Ibid,  xxxviii.  13.  3  Ibid.  xli.  107. 

4  Ibid.  xlii.  215.  8  Ibid.  Ixvi.  197. 

6  Compt.  Rend.  Trav.  Chim.  1849,  222. 

7  Ann.  Chem.  Pharm.  Ixxv.  12. 

8  Revue  Scient.  xiv.  560  ;  Compt.  Rend.  xxi.  36. 

9  Ber.  Deutsch.  Chem.  Oes.  i.  125. 

10  Zeitschr.  Chem.  x.  419  ;  Ann,  Chem.  Pharm.  cxliv.  71. 


THE  PHTHALIO  ACIDS.  451 

in  1847,  by  heating  oil  of  turpentine  (essence  de  te're'benthine) 
with  dilute  nitric  acid,  and  named  on  this  account  terephthalic 
acid  (acide  terephtahque).1  Five  years  previously,  Persoz  had 
obtained  cumino-cyminic  acid  (acide  cumino-cyminique)  by  the 
oxidation  of  the  ethereal  oil  contained  in  the  seeds  of 
Roman  cumin  (Cuminum  Cyminum},  but  had  not  analysed  it.2 
Hofmann,  in  attempting  to  purify  cumic  acid,  C10H12O2,  by 
treatment  with  dilute  sulphuric  acid  and  potassium  dichromate, 
found  that  it  is  thus  oxidized  to  insolinic  acid,  C9H804,  which  he 
also  obtained  from  Roman  cumin  oil,  and  which,  as  he  pointed 
out,  is  very  similar  to  terephthalic  acid,3  these  being  afterwards 
shown  by  H.  Miiller  and  Warren  de  la  Rue  to  be  identical.4 

Fittig  then  prepared  a  third  acid  by  the  oxidation  of  isoxylene 
and  named  it  isophthalic  acid.5 

The  methods  employed  in  the  determination  of  the  position  of 
the  carboxyl  groups  in  these  three  acids  have  already  been 
described  in  detail  (Part  III.,  p.  38).  Quite  recently,  however, 
Nolting  has  added  a  very  simple  proof  of  their  constitution. 
The  three  acids  can  be  quantitatively  obtained  by  the  oxidation 
of  the  three  dimethylbenzenes  with  an  alkaline  solution  of 
potassium  permanganate.  Paraxylene  yields  terephthalic  acid 
and  on  nitration  gives  only  one  mononitroxylene,  while  ortho- 
xylene  is  oxidized  to  phthalic  acid  and  yields  two  nitre-deriva- 
tives. Finally,  three  nitroxylenes  can  be  obtained  from  isoxylene, 
which  corresponds  to  isophthalic  acid.  The  position  of  the 
carboxyls  is,  therefore,  in  : 

Phthalic  acid 1:2 

Isophthalic  acid 1:3 

Terephthalic  acid 1:4 

This  proof  is  exactly  analogous  to  that  employed  by  Korner 
to  determine  the  positions  of  the  bromine  atoms  in  the  three 
dibromobenzenes,  and  by  Griess  in  ascertaining  the  constitution 
of  the  diamidobenzenes  (Part  III.,  pp.  47,  48).6 

1  Ann.  Chim.  Phys.  [3]  xxi.  28. 

2  Journ.  PraU.  Chem.  xxiv.  55  ;  Compt.  Rend,  xxxiii.  433. 

3  Ann.  Chem.  Pharm.  xcvii.  197. 

4  Ibid.  cxxi.  86.  5  Ibid,  cxlviii.  11. 
c  Ber.  Deutsch.  Chem.  Ges.  xviii.  2687. 


452  AROMATIC  COMPOUNDS. 


PHTHALIC  ACID. 

2240  This  acid  is  most  simply  formed  by  the  oxidation  of 
orthoxylene  or  orthotoluic  acid  1  with  potassium  permanganate 
or  dilute  nitric  acid.2  Carius  found  that  it  is  also  obtained  in 
small  quantity  when  benzene  or  benzoic  acid  is  treated  with 
manganese  dioxide  and  concentrated  sulphuric  acid  in  the  cold,3 
diphenylbenzene,  C6H4(C6H5)2,  being  probably  the  intermediate 
product  (Part  III.,  p.  76).  According  to  Guyard,  it  is  also  formed 
when  a  mixture  of  salicylic,  formic  and  sulphuric  acids  is 
heated.4 

Phthalic  acid  is  manufactured  from  naphthalene,  C10H8, 
which  is  first  converted  into  the  tetrachloride,  C10H8C14,  by 
passing  chlorine  through  the  fused  hydrocarbon,  the  plant  shown 
in  section  and  elevation  in  Figs.  2  and  3  being  employed.  The 
mass  becomes  heated  to  such  an  extent  that  the  iron  vessel 
containing  it  has  to  be  cooled  by  water,  the  temperature  being 
kept  below  160° — 170°,  above  which  carbonization  takes  place. 
The  tetrachloride  is  also  manufactured  by  grinding  naphthalene 
with  water  and  potassium  chlorate,  making  up  the  paste  into 
balls,  and  bringing  these,  after  drying,  into  concentrated  hydro- 
chloric acid.  The  chlorate  may  be  replaced  by  bleaching 
powder  which  is  mixed  with  naphthalene  and  pressed  into 
cakes. 

One  part  of  the  chloride  is  then  heated  with  5 — 6  parts  of 
nitric  acid  of  sp.  gr.  1*35  in  flat  stoneware  retorts  placed  in  an 
air-bath  (Figs.  4  and  5). 

The  vapours  which  are  evolved  are  condensed  and  employed 
in  a  subsequent  operation.  The  acid  may  be  finally  purified 
by  crystallization,  but  the  product  is  usually  distilled  and  thus 
immediately  converted  into  the  anhydride.  The  yield  amounts 
to  30  per  cent,  on  the  naphthalene.5 

Phthalic  acid  is  also  formed  when  naphthalene  is  heated  to 
130°  with  20  parts  of  nitric  acid  of  sp.  gr.  I'lo,  40  percent  of 
the  theoretical  yield  being  obtained.6 

1  Weith,  Ber.  Deutsch.  Ckcm.  Ges.  vii.  1057.     2  Piocard,  ibid.  xii.  579. 
3  Ann.  Chem.  Pharm.  cxlviii.  60.  4  Bull.  Soc.  Chim.  xxix.  248. 

e  Schultz,  Stcinkohlentkecr,  S.   540  ;  s.   E.   Fischer,   Ber.  Deutsch.   Chem.  Ges. 
xi.  735  ;  Depouilly,  Ann.  Chem.  Pharm.  cxxxvii.  373. 
6  Beilstein  and  Kurbatow,  Ann.  Chem.  Pharm.  ccii.  215. 


PHTHAL1C  ACID. 


453 


i 


260 


454 


AROMATIC  COMPOUNDS. 


PHTHALIC  ACID. 


455 


Properties.  It  crystallizes  from  hot  water  in  thin  plates  or 
lustrous,  rhombic  prisms,1  which  dissolve  in  130  parts  of  water 
at  11-5°. 


100  parts  of 

dissolve  at  15° 


ether 


absolute  alcohol    90  per  cent,  alcohol, 

10-08  11-70  parts.2 


FTG.  4. 


Varying  statements  have  been  made  as  to  the  melting-point 
of  the  acid,  the  discrepancies  being  due  to  the  fact  that  it  loses 
water  on  heating,  the  anhydride  being  formed.  According  to 

1  Scheibler,  Ser.  Deutsch.  Chem.  Ges.  i.  125;  Groth,  Jahresber.  Chem.  1870,  5. 

2  Bourgoin,  Bull.  Soc.  Chim.  xxix.  247. 


456 


AROMATIC  COMPOUNDS. 


Lessen,    this   takes  place  at  184°,  while  Ador  states  that  the 
unbroken  crystals  melt  at  213°,  but  the  powder  at  2030.1 

It  is  completely  burned  by  chromic  acid  solution  on  heating,2 
and  on  this  account  cannot  be  prepared  by  means  of  this  reagent 
from  orthoxylene  or  other  ortho-compounds  which  possess  two 
side  chains.  On  distillation  with  lime  it  decomposes  into  carbon 


FIG.  5. 

dioxide  and  benzene,  but  if  the  temperature  be  not  allowed  to 
rise  above  330° — 350°,  it  is  converted  into  benzoic  acid,  which 
was  formerly  manufactured  in  this  way  (p.  155). 

2241  The  normal  phthalates  of  the  alkali  metals  are  readily 
soluble  in  water  and  crystallize  in  small  plates  or  scales. 

Acid  ammonium  phthalate,  C8H504(NH4),  separates  on  the 
spontaneous  evaporation  of  a  solution  of  the  normal  salt  in  six- 

1  Ann.  Chem.  Pharm.  clxiii.  230.  2  Fittig  and  Bieber,  ibid.  clvi.  242. 


SALTS  OF  PHTHALIC  ACID.  457 

sided,  rhombic  tablets,  prisms  or  pyramids,  which  dissolve  very 
readily  in  water  but  only  slightly  in  alcohol. 

Calcium  phthalate  C8H4O4Ca-f-H2O,  is  tolerably  soluble  in 
water  and  crystallizes  in  lustrous,  rhombic  prisms.1 

Acid  barium  phthalate,  (C8H5O4)2Ba,  is  readily  soluble  in  hot 
water  and  crystallizes  in  small,  rhombic  prisms. 

Normal  barium  phthalate,  C8H4O4Ba,  is  obtained  by  preci- 
pitating the  normal  ammonium  salt  with  barium  chloride,  or  by 
mixing  hot  solutions  of  the  acid  and  caustic  baryta  ;  it  forms 
small,  white  scales  or  silky  needles,  which  are  only  slightly 
soluble  in  hot  water.  On  evaporating  the  solution,  a  basic  salt 
separates  out  in  crystalline  crusts  (Carius,  Hermann). 

Lead  phthalate,  C8H4O4Pb,  is  a  precipitate,  consisting  of  scaly 
crystals. 

Copper  phthalate,  C8H4O4Cu  +  H2O,  crystallizes  in  lustrous 
blue,  rhombic  prisms,  which  dissolve  readily  in  hot  water 
(Hermann). 

Silver  phthalate,  C8H4O4Ag2,  forms  a  light,  crystalline  powder, 
which  is  tolerably  soluble  in  water  and  detonates  when  rapidly 
heated. 

JZthers  ofphthalic  acid  are  formed  by  the  action  of  hydrochloric 
acid  on  the  alcoholic  solution  of  the  acid  and  by  that  of  an  alco- 
holic iodide  upon  the  silver  salt.  The  two  following  have  been 
prepared,  and  are  both  odourless  liquids  :  2 

Boiling-point. 

Methyl  phthalate,  C6H4(C02.CH3)2  .....  280° 

Ethyl  phthalate,  C6H4(C02.C2H5)2    .    .    .  294° 

Phthalyl  oxide  or  Phthalic  anhydride,  (C6H4.C02)2O,  is  formed 
when  the  acid  is  heated  alone  or  with  acetyl  chloride  : 


CO.OH 

+  CH8.COC1  = 

C0 


C6H4<  +  CH8.COC1  = 

\CO.OH 


.OH  +  HC1. 


The  anhydride  remains  behind  in  splendid  prisms  after  the 
acetic  acid  and  excess  of  acetyl  chloride  have  been  removed.3 
It  is  manufactured  by  subliming  phthalic  acid  in  a  current  of 

1  Hermann,  Ann.  Chetn.  Pharm.  cli.  77. 

2  Grabe  and  Born,  ibid,  cxlii.  344  ;  Grabe,  Bcr.  Deutsch.   Chcm.  Ges.  xvi.  860. 

3  Anschiitz,  ibid.  x.  235  ;  Ann.  Chem.  Pharm.  ccxxvi.  1. 


458  AROMATIC  COMPOUNDS. 

air,  or  better,  of  carbon  dioxide,  the  apparatus  shown  in  Fig.  6 
being  employed.1 

It  is  thus  obtained  in  long,  white,  pliant,  rhombic  needles, 
while  on  rapid  heating  it  distils  as  a  liquid  and  then  solidifies 
to  a  hard,  crystalline  mass.  It  melts  at  128°  and  boils  at  284'5° 
(Schultz,  Griibe),  is  only  very  slightly  soluble  in  cold,  more 
readily  in  hot  water,  and  is  reconverted  into  phthalic  acid  when 
boiled  with  water  for  a  long  time,  more  rapidly  in  presence  of 
alkalis. 

It  is  reduced  by  zinc  dust  and  acetic  acid  to  phthalide,  di- 
phthalyl  (v.  post)  and  zinc  phthalate  being  also  formed.2  It  is 
employed  in  the  manufacture  of  dyes  and  of  many  other  com- 
pounds, as  it  very  readily  enters  into  chemical  reactions.  Thus 
it  combines  with  the  acid  anhydrides,  forming  with  acetic 

XC=CH.C0.2H 
anhydride,  phthalylacetic  acid,  C6H4<^    >O 

It  also  combines  with  the  aromatic  hydrocarbons  in  presence  of 
aluminium  chloride,  forming  acids  ;  thus  benzene  yields  benzoyl- 
benzoic  acid  : 

/COV  /CO.OH 

C6H4<        >0  +  C6H6  =  C6H4<; 

\C(K  \CO.C6H5. 

A  specially  characteristic  property  is  that  of  combining  with 
phenols  on  heating  to  form  pkthale'ins,  water  being  eliminated. 
As  already  mentioned,  resorcinol  yields  fluorescent  in  this  way, 
the  formation  of  this  substance,  which  is  employed  as  a  test  for 
the  presence  of  the  phenol  in  question,  taking  place  in  the 
following  manner  : 


CO  C\CH° 

I      ^en4 


I 

e4  +  2C6H4<g  =  C6H0  X)H  +  2H20. 

CO  CO 

2242  PJithalyl  chloride,  C8H4O2C12,  was  first  prepared  by  Hugo 
Miiller  from  phthalic  acid  by  the  action  of  phosphorus  penta- 

1  Schultz,  Sleinkohlcntheerc. 

2  Wislicenus,  Ber.Deutsch.  Chem.  Gcs.  xvii.  2178. 


PHTHALYL  CHLORIDE. 


459 


!3  2 

er-     0} 

*^     > 


W     fcc-M 

H     5   S 


O 

S.*3 


CO     Eo'd 
S    >23  g" 

EH     43          j3 
N'ff 

B  III 


SS1§ 
3  *>a 


ft 


1 1' 

e5  &: 


-f 

0  g  l 
Bit 


460  AROMATIC  COMPOUNDS. 

chloride.1     From  analogy  with  other  acid  chlorides  it  would  be 
formed  according  to  the  following  equation  : 

/CO.OH  /COC1 

C6H4<  +  2PC15  =  C6H4<  +2POC13  +  2HC1. 

\CO.OH  \COC1 

Careful  investigation,  however,  has  shown  that  it  does  not 
possess  this  constitution.     It  is  formed  in  two  stages  : 

/CO.OH  /COV 

C0H4<  +  PC15  =  C6H4<        >0  +  POC13  +  2HC1. 

\CO.OH  Nxx^ 


/c<\ 

C6H4<        >0  +  PC15  =  C6H4<          >0  +  POOL, 
\CCK  \  CO  / 


It  is  also  obtained,  therefore,  when  equal  molecules  of  phthalic 
anhydride  and  phosphorus  pentachloride  are  heated  together  for 
12  hours  at  1700.2 

In  order  to  prepare  it,  phthalic  acid  is  boiled  with  rather  more 
than  two  molecules  of  phosphorus  chloride  for  5-6  hours  and 
then  distilled.3  It  is  an  oily  liquid,  which  boils  at  268°  arid 
solidifies  at  about  0°.  It  is  only  slowly  decomposed  by  boiling 
water  and  even  boiling  caustic  soda  solution.  On  heating  with 
finely-divided  silver,  diphthalyl,  which  will  be  subsequently 
described,  is  obtained,  its  formation  taking  place  according  to 
the  following  equation  : 

/  co  \  /co\ 

C'H<cc,>  C'H<c> 

+  4Ag=  ||  +4AgCL 

s    C    v 


C6H4  0  C6H4  0 


The  proof  that  it  possesses  this  constitution,  rests  not  only  on  the 
whole  behaviour  of  the  substance,  which  shows  it  to  be  a  dilac- 

1  Zeitschr.  Chem.  1863,  257. 

2  Claus  and  Hoch,  Bcr.  Dcutach.  Chem.  Ges.  xix.  1187. 

3  Wischin,  Ann.  Chem.  Pharm.  cxliii.  259. 


PHTHALYL  CHLORIDE. 


461 


tone,  but  also  on  the  fact  that  it  is  formed  when  phthalide  is 
heated  with  phthalic  anhydride  : 1 


,00 


/°°\ 

C6H/      >0 


H2O. 


The  following  compounds  have  been  prepared  by  the  action 
of  sodium  methylate  and  ethylate  on  phthalyl  chloride  : 


/C(OCH3)2 
/>0 


Boiling-point. 

280° 


294' 


co 


These  are  liquids  which  boil  at  the  same  temperature  as  the 
isomeric  phthalic  ethers,  from  which  they  differ  only  in  possess- 
ing a  slightly  lower  specific  gravity.  That  they  are  actually 
distinct  bodies  is  shown  by  the  fact  that  tetrachlorophthalic  acid 
yields  compounds  which  differ  both  in  crystalline  form  and  melt- 
ing point  from  those  derived  from  its  chloride.2 

The  corresponding  phenyl  ether,  C6H4(CO)C(OC6H5)2O,  is 
prepared  by  heating  the  chloride  with  phenol,  and  crystallizes 
from  alcohol  in  small  prisms,  melting  at  70°.3 

When  phthalyl  chloride  is  heated  in  a  sealed  tube  with 
phosphorus  pentachloride  to  210° — 220°,  two  isomeric  chlorides, 
C8H4C14O,  are  formed,  both  of  which  crystallize  in  monosyrn- 
metric  forms ;  the  one  melts  at  47°,  and  the  other,  which  is  also 
a  product  of  the  action  of  phosphorus  pentachloride  on  phthalide, 
at  88°.  Theory,  indeed,  allows  the  formation  of  two  isomeric 
tetrachlorides  : 

/cci2;  /coci 

r,  H  '        \o  r  TT  / 

6  4\cci /°  °A\cci8. 

The  compounds  in  question,  however,  exhibit  an  identical 
chemical  behaviour.  On  heating  with  concentrated  sulphuric 
acid,  or  on  boiling  with  alcoholic  potash,  they  are  converted  into 

1  Grabe  and  Guye,  Ber.  Deutsch.  Chcm.  Ges.  xvii.  2851. 

2  Grabe,  Ber.  Deutsch.  Chem.  Ges.  xvi.  860. 

3  Schreder,  ibid.  vii.  705  ;  v.  Gerichten,  ibid.  xiii.  419. 


462  AROMATIC  COMPOUNDS. 

phthalic  acid,  and  phenol  combines  with  them  to  form  the  phenyl 
ether  mentioned  above.  These  facts  seem  to  indicate  a  case  of 
physical  isomerism,  but  all  endeavours  to  convert  either  of  the 
compounds  into  the  other  have  proved  unsuccessful  (v.  Gerichten). 

According  to  Glaus  and  Hoch,  the  tetrachloride,  which  melts 
at  88°  and  boils  at  about  274°,  is  alone  obtained  and  is  best 
prepared  by  heating  for  15  hours  at  245°.  Carbonyl  chloride 
and  orthochlorobenzoyl  chloride  are  also  formed  in  the  reaction.1 

A  compound  is  formed  by  the  action  of  zinc  ethyl  on  phthalyl 
chloride,  which  is  looked  upon  by  Wischin  as  phenylenediethyl- 
acetone,  C6H4(CO.C2H5)2.  It  separates  from  ethereal  solution  in 
splendid  crystals,  which  possess  a  pleasant,  fruity  smell,  and 
melt  at  52°.  Wischin  was,  however,  unable  to  obtain  a  com- 
pound of  it  with  acid  sodium  sulphite,  and  V.  Meyer  has  shown 
that  it  is  not  a  ketone,  since  it  does  not  form  a  hydroxylamine 
compound.2  The  constitution  of  this  compound  can  readily  be 
explained  in  accordance  with  the  present  views  in  regard  to 
phtbalyl  chloride,  and  is  as  follows  : 


/ 

C«H<co> 

Succinyl  chloride  (Part  II.,  p.  191)  has  obviously  an  analogous 
constitution  to  phthalyl  chloride,  and  its  reduction  to  the 
anhydride  or  lactone  of  7-hydroxybutyric  acid  (Part.  II.,  p. 
169)  thus  receives  a  simple  explanation  : 

/  2\  /^-*-*-2\ 

C  A<T        '  >0  +  4H  =  C2H4<         '  >0  -t  2HC1. 
XCO  '  \CO  ' 

Phthalyl  sulphide  or  Thiophthalic  anhydride,  C8H402S,  is 
formed  by  the  action  of  potassium  hydrosulphide  on  phthalyl 
chloride  3  or  its  phenyl  ether  :  4 

CC1  C*S 

C6H4<f        NO  +  2KSH  =  C6H  /      NO  +  2KC1  +  SH9. 
\  CO  /  \CO/ 

It  crystallizes  from  alcohol  in  small  plates  or  needles,  melts  at 
114°  and  boils  at  284°. 

1  Bcr.  Dfiutsch.  CJiem.  Ge*,  xix   1137.      2  Ibid.  xvii.  817. 

8  Schreder,  ibid.  vii.  705.  4  Griibe  and  Zschokke,  ibid.  xvii.  1175. 


PHTHALAMIC  ACID.  463 


2243  Phihalimide,  C8H4O2(NH),  is  obtained  by  heating  acid 
ammonium  phthalate : 1 

XCO.ONH4  >  C=NH 

C6H/  =C6H4<(    >0+H,0. 

\CO.OH  \CO 

It  is  also  formed  by  the  action  of  ammonia  on  the  anhydride, 
chloride,2  or  sulphide,3  as  well  as  by  heating  phthalic  acid  with 
ammonium  or  potassium  thiocyanates.4  It  is  insoluble  in  cold 
water,  slightly  soluble  on  boiling,  and  crystallizes  from  ether  in 
six-sided  prisms,  which  melt  at  228° 5  and  sublime  in  small  plates. 
It  is  decomposed  on  heating  with  slaked  lime  into  carbon 
dioxide  and  benzonitril,6  and  is  reduced  to  phthalimidine  (p.  444) 
>y  tin  and  hydrochloric  acid. 

When  phthalimide  is  heated  with  aniline  or  one  of  its 
homologues,  ammonia  is  evolved  and  the  corresponding  substi- 
tuted phthalimide  formed.  If  a  phenol  be  substituted  for  the 
amine,  ammonia  is  also  evolved,  and  a  substance  belonging  to 
the  class  of  phthaleins  is  produced. 

These  bodies  are  identical  with  those  prepared  from  phthalic 
anhydride.7 

Potassium  phthalimide,  C8H400(NK),  is  obtained  in  white 
plates  by  adding  alcoholic  potash  to  an  alcoholic  solution  of  phthal- 
imide (Cohn). 

Silver  phthalimide,  C8H402(NAg),  is  formed  as  a  heavy,  white 
precipitate  when  silver  nitrate  is  added  to  an  aqueous  solution  of 
the  potassium  salt,  or  when  an  alcoholic  solution  of  phthalimide 
is  treated  with  an  ammoniacal  silver  solution  (Laurent). 

Phthalamic  acid,  C6H4(CO.NH2)CO2H.  Marignac  prepared 
the  ammonium  salt  of  this  acid  by  dissolving  anhydrous  naph- 
thalic  acid  (phthalic  acid)  in  ammonia,  and  named  it  naphthal- 
amide.8  It  was  also  obtained  by  Laurent,  who  added  ammonia  to 
a  hot,  alcoholic  solution  of  the  anhydride  . 9 

/CO.  /CO.NH2 

C6H4<        >0  +  2NH3  =  C6H4< 

\CO/  \CO.ONH4 

1  Laurent,  Ann.  Chem.  Pharm.  xli.  110. 

2  Kuhara,  Amer.  Chem.  Journ.  iii.  26. 

3  Grabe  and  Zschokke,  loc.  cit. 

4  Ossian  Aschan,  Ber.  Deutsch.  Chem.  Gcs.  xix.  1398. 
6  Cohn,  Ann.  Chem.  Pharm.  ccv.  301. 

6  Laurent,  Jahrcsb,  Chem.  1868,  549. 

7  Hall,  Private  Communication. 

8  Ann.  Chem.  Pharm.  xlii.  219. 

»  Ann.  Chim.  Phys.  [3]  xxiii.  117. 


464  AROMATIC  COMPOUNDS. 

The  barium  salt  is  formed  when  phthalimide  is  boiled  with 
baryta  water  (Kuhara),  and  the  potassium  salt  by  the  continued 
boiling  of  potassium  phthalimide  with  water.1  It  may  be  more 
simply  prepared  by  the  action  of  25  per  cent,  caustic  potash 
solution  on  phthalimide.2  When  concentrated  hydrochloric  acid 
is  added  to  the  solution,  the  phthalamic  acid  is  gradually  deposited 
in  short,  well  developed,  transparent  prisms,  which  melt  at  148°— 
149°  and  decompose  at  a  slightly  higher  temperature  into  water 
and  phthalimide.  It  has  an  acid  taste,  is  tolerably  soluble  in  cold 
water  and  is  gradually  converted  by  it  into  acid  ammonium 
phthalate,  the  change  taking  place  rapidly  on  boiling  (Aschan). 

Ethyl  phthalimide,  C6H4O2(NC2H5),  is  prepared  by  the  distilla- 
tion of  phthalic  anhydride  with  aqueous  ethylamine;  it  crystal- 
lizes in  needles  or  prisms,  melts  at  78'5°  and  boils  at  276°  —  2780.4 

Acetphthalimide,  C8H4O2(NCO.CH3),  is  formed  by  heating 
phthalimide  with  acetic  anhydride  for  some  time.  It  crystallizes 
in  large  octohedra  and  is  decomposed  by  boiling  water  or  by 
alkalis  in  the  cold  into  acetic  acid  and  phthalimide.5 

Phthaluric  acid  is  obtained  by  heating  phthalic  anhydride 
with  amido-acetic  acid  : 

/C0\ 
C6H4<         )0  +  NH2.CH2.C0.7H  = 

XXX 

XC=N.CH2.C02H 

>0  +H20. 


It  crystallizes  from  hot  water  in  long,  thin  needles,  which 
melt  at  191°  —  192°,  and  are  decomposed  on  boiling  with  con- 
centrated hydrochloric  acid  into  phthalic  and  amido-acetic  acids.6 

Phenylphtlialimide  or  Phthalanil,  C8H402(NC6H5),  is  prepared 
by  distilling  phthalic  acid  with  aniline;  it  crystallizes  from 
alcohol  in  needles,  which  melt  at  205°,  but  sublime  at  a  lower 
temperature.7  On  boiling  with  ammonia  and  alcohol,  it  is  con- 
verted into  phtlialanilic  acid,  or  phenylphthalamic  acid  : 

/C=NC6H5  /CO.  NH.  C6H5 

C6H4<    >0          +  H20=C6H/ 

\CO  NCO.OH. 

1  Landsberg,  Ann.  Chem.  Pharm.  ccxv.  198. 

2  Ossian  Aschan,  Ber.  Deutsch.  Chem.  Gcs.  xix.  1401. 

3  Michael,  ibid.  x.  1646.  4  Wallach  and  Kamenski,  ibid.  xiv.  171. 
6  Ossian  Aschan,  ibid.  xix.  1400. 

6  Drechsel,  Journ.  Prakt.  Chem.  [2]  ccxxvii.  418. 

7  Gerhardt  and  Laurent,  Ann.  Chem.  Phys.  [2]  xxiv.  189  ;  Dbbner,  Ann.  Chem. 
Pharm.  ccx.  267. 


DIPHENYLPHTHALEIN.  465 

This  substance  crystallizes  from  hot  water  or  alcohol  in  small 
plates,  which  melt  at  192°  and  decompose  into  water  and 
phthalanil  at  a  higher  temperature. 

Analogous  compounds  are  obtained  from  the  substitution 
products  of  aniline 1  and  its  homologues,2  from  the  amido- 
phenols,3  and  from  the  amidobenzoic  acids.4 

Diphenylphthalamic  acid  is  formed  when  equal  molecules  of 
phthalic  anhydride  and  diphenylamine  are  heated  together : 


It  is  insoluble  in  water  and'  crystallizes  from  alcohol  in  warty 
masses  of  small,  lustrous  prisms,  which  melt  at  147°  —  1480.5 

If  two  molecules  of  diphenylamine  are  employed,  the  so-called 
diphenylphthale'in  is  formed;  it  is  also  obtained  by  the  action 
of  the  base  on  phthalyl  chloride,6  and  is  tolerably  soluble  in 
alcohol,  more  readily  in  benzene,  from  which  it  crystallizes  in 
large  prisms,  melting  at  238°.  It  has  the  following  constitu- 
tion : 


The  aromatic  diamines  form  two  series  of  compounds  with 
phthalic  anhydride  :  7 

XC=N.C6H4.  NH2  XC=H.  C6H4.N=CX 

C6H4<    >0  -C6H4<(   >0  0<    ^C6H4. 

\CO  \CO  CO/ 

When  orthamidothiophenol  is  heated  with  phthalic  anhydride 
or  phthalyl  chloride,  the  compound  C20H12N2S2  is  formed,  and 
probably  has  the  following  constitution  : 

N.  K. 


1  Gabriel,  Bcr.  Dcutsch.  Chcm.  Gcs.  xi.  2260  ;  Frohlich,  ibid.  xvii.  1801  and 
2679.  2  Michael,  ibid.  x.  579. 

3  Ladenburg,  ibid.  ix.  1528.  4  Gabriel  loc.  cit. 

Piutti,  Gaz.  Chim.  Ital.  xiii.  542  ;  xiv.  470. 

6  Lellmann,  Bcr.  Deutsch.  Chem.  Ges.  xv.  830. 

7  Biedermann,  ibid.  x.  1160. 


466  AROMATIC  COMPOUNDS. 

It  crystallizes  from  alcohol  in  thin  needles  or  thick  prisms, 
which  melt  at  112°;  it  is  a  weak  base  and  forms  a  hydrochloride 
which  is  only  slightly  soluble  and  crystallizes  well,  but  is  readily 
decomposed  by  water.1 

2244  PhtJialyldiamide.  Phthalylmalonic  ether  is  formed  by 
the  action  of  phthalyl  chloride  on  sodmalonic  ether,  and  reacts 
with  ammonia  to  form  malonamide,  alcohol  and  phthalyldi- 
amide  :  2 

XC=C(CO.OC2H5)2 
C6H4      >0  +4NH3  = 


/  C     - 
CH2(CO.NH2)2  +  2HO.C2H5  +  C6H4< 


This  body  may  also  be  obtained  in  a  similar  manner  from 
phthalylaceto-acetic  ether,3  and  by  allowing  phthalimide  to 
stand  for  some  hours  in  contact  with  concentrated  ammonia/ 
It  forms  a  glittering  powder,  consisting  of  microscopic,  very 
refractive  rhombohedra,  only  slightly  soluble  in  water  and 
alcohol,  and  is  decomposed  into  ammonia  and  phthalimide 
when  heated  with  either  of  these.  It  fuses  at  219°  —  220°,  when 
carefully  heated,  forming  a  clear  liquid,  but  ammonia  is  given 
off  and  the  residue  finally  consists  of  phthalimide. 

Phthalylliydroxylamine,  N(C8H4O9)OH,is  formed  when  phthalyl 
chloride  and  sodium  carbonate  are  alternately  added  to  a  con- 
centrated solution  of  hydroxylamine  hydrochloride,  so  that  the 
liquid  is  always  kept  alkaline  : 

/CC12  C=N.OH 


C6H4<  >0  +  H2N.OH  =  C6H4<     >O         +  2HC1. 

\CO/  \CO 

It  is  insoluble  in  ether,  but  dissolves  slightly  in  water,  more 
readily  in  boiling  alcohol,  from  which  it  crystallizes  in  small 
plates  or  needles,  which,  after  drying,  form  a  yellow  powder, 
melting  at  230°  with  decomposition.  It  is  an  acid,  decomposes 
carbonates  and  forms  a  red  solution  in  alkalis.  Alcoholic  potash 

1  Hofmann,  Ber.  Deutsch.  Chem.  Ges.  13,  1233. 

2  Wislicenus,  ibid.  xvii.  Eef.  529. 

3  Billow,  Ann.  Chem.  Pharm..  ccxxxvi.  188. 

4  Ossian  Oschan,  Bcr.  Deutsch.  Chem.  Ges.  xix.  1398. 


ETHYLPHTHALYLHYDROXYLAMINE.  467 

added  to  its  solution  in  alcohol  precipitates  the  potassium  salt, 
N(C8H4O2)OK,  which  consists,  as  does  the  sodium  compound,  of 
an  amorphous  red  powder.  The  silver  compound  is  obtained  by 
double  decomposition  as  a  dark-red  precipitate,  the  barium  and 
lead  salts  being  light  red  and  yellowish  red  precipitates,  while  the 
copper  salt,  which  is  only  thrown  down  from  a  concentrated  solu- 
tion, is  green,  and  the  aluminium  and  mercury  salts  are  yellow. 

Ethylphthalylhydroxylamine,  N(C8H4O2)OC2H5,  is  obtained  by 
treating  the  silver  salt  with  ethyl  iodide.  It  forms  large  crystals 
which  melt  at  103°— 104°  and  boil  at  270°. 

Phthalylhydroxylamine  decomposes  on  dry  distillation  into 
phthalic  anhydride,  ammonia  and  nitrogen;  a  boiling  solution 
of  caustic  potash  resolves  it  into  phthalic  acid  and  hydroxylamine, 
while  orthamidobenzoic  acid  is  formed  when  it  is  heated  in 
alcoholic  solution  with  one  molecule  of  potash  : 

/C=N.OH  /NH2 

C6H4<    >0  +  KOH  =  C6H4<  +C02. 

\CO  \CO.OK 

Hydroxyphthalamic  acid  is  formed  when  an  alcoholic  solution 
of  phthalylhydroxylamine  is  heated  with  potash  for  a  short  time  : 

/C=N.OH  /CH=N.OH 

C6H4<    >0        +KOH=C6HX 

X)0  XXXOK 

Potassium  hydroxypkthalamate  separates  out  on  cooling ;  it 
is  readily  soluble  in  water,  and  is  deposited  on  evaporation  in 
hard,  yellow  crystals. 

The  lead  salt  is  thrown  down  when  lead  acetate  is  added  to  a 
solution  of  the  potassium  salt ;  it  has  the  following  constitution  : 

/CH=N.(\ 

P  TT  /  \PV» 

<^6-ti4\  /rb. 

\00 O/ 

When  this  is  suspended  in  water  and  treated  with  sulphuretted 
hydrogen,  a  solution  of  the  free  acid  is  formed,  which  reddens  lit- 
mus and,  like  that  of  the  potassium  salt,  is  coloured  violet  by  ferric 
chloride.  The  solution  of  the  acid  decomposes  gradually  on 
standing,  more  rapidly  when  heated,  with  separation  of  phthalyl- 
hydroxylamine. 

Phthalylhydroxylamine  shows  great  similarity  to  the  nitrolic 


468  AROMATIC  COMPOUNDS. 

acids,  which,  like  the  former,  are  colourless  but  are  coloured  red 
by  the  slightest  trace  of  an  alkali,  and  have  a  similar  constitu- 
tion : L . 

Phthalylhydroxylamine  Ethylnitrolic  acid. 


cy3-4\  >o 

xco 

Benzenylazoximebenzenylcarboxylic  acid,  C15H10N2O3,  is  formed 
when  phthalic  anhydride  is  fused  with  benzenylamidoxime  : 

^N.OH 

C6H6,< 


C6H6.C^      ^C.C6H4.C02H+H20. 

It  crystallizes  from  hot  alcohol  in  lustrous  needles  melting  at 
1510.2 

OrtTiocyanobenzoic  acid,  C6H4(CN)CO2H,  is  obtained  by  adding 
orthodiazobenzoyl  chloride  to  a  hot  solution  of  copper  sulphate 
and  cuprous  cyanide  ;  it  is  a  thick,  viscous  liquid,  which  has  not 
hitherto  been  prepared  pure,  since  it  readily  changes  into  the 
isomeric  phthalimide,  phthalamic  acid  being  probably  formed 
as  an  intermediate  product : 

<HN"  PO  NTT 

CH/       -       +HO  =  CH/ 

\CO.OH  \CO.OH ' 

This  is  then  resolved  into  phthalimide  and  water.3 
The   conversion  may   however  be   simply   explained   by   an 
intermolecular  change : 4 


C6H4  =C6H4<;    >0    . 

\CO-OH  \CO 

Ethyl  orthocyanobenzoate,  C6H4(CN)CO2.C2H5,  is  prepared  by 
diazotizing  the  ethyl  ether  of  orthamidobenzoic  acid  and  treating 
the  product  in  the  manner  just  described;  it  crystallizes  in 
thick  needles,  melting  at  70°.5  It  is  gradually  attacked  when 

1  Cohn,  Ann.  Chem.  Pharm.  ccv.  295. 

2  Schulz,  Ber.  Deutscli.  Chem.  Ges.  xviii.  2463. 

3  Sandmeyer,  ibid,  xviii.  1496.  4  Liebermann,  ibid.  xix.  2283. 
5  Muller,  ibid.  xix.  1491. 


DIHYDROPHTHALIC  ACID.  469 

heated  with  hydroxylamine  in  alcoholic  solution,  phthalimide- 
oxime  being  formed  : 

C=N 


/ 
C6H4<  +  H2N.OH  =  C6H       >0        +  HO.C2H5. 


\CO.OC2H5 

The  latter  crystallizes  from  dilute  alcohol  in  needles,  which 
melt  at  250°  and  are  converted  into  phthalimide  by  boiling  with 
ferric  chloride  and  hydrochloric  acid. 


ADDITION  PRODUCTS  OF  PHTHALIC  ACID. 

2245  Dihydrophthalic  acid,  C6H6(C02H)2,  is  formed  when  a 
cold  alkaline  solution  of  phthalic  acid  is  treated  with  sodium 
amalgam,1  or  better  when  the  operation  is  carried  on  at  the 
boiling  point.2  It  crystallizes  in  hard,  rhombic  tablets,  which 
are  only  slightly  soluble  in  cold,  more  readily  in  hot  water,  and 
readily  in  alcohol.  It  is  a  strong  dibasic  acid ;  on  heating  with 
soda  lime  it  decomposes  into  carbon  dioxide,  hydrogen  and 
benzene,  while  the  action  of  phosphorus  pentachloride  upon  it 
yields  hydrochloric  acid,  carbon  dioxide,  phosphorus  oxychloride 
and  benzoyl  chloride.  Bromine  acts  upon  its  aqueous  solution 
in  the  following  manner  (Grabe  and  Born) : 

C6H6(C02H)2  +  Br2  =  C6H5.C02H  +  CO2  +  HBr. 

On  heating  with  sulphuric  or  nitric  acids,  ben  zoic  acid  is  also 
formed,  together  with  phthalic  acid,  while  ethyl  benzoate,  pro- 
bably accompanied  by  ethyl  formate,  is  produced  when  hydro- 
chloric acid  is  passed  into  its  alcoholic  solution. 

Hydrophthalic  acid  can  be  heated  to  200°  without  undergoing 
any  alteration  ;  at  a  higher  temperature,  however,  it  decomposes 
with  formation  of  phthalic  anhydride. 

All  these  reactions  may  be  simply  explained  if  we  ascribe  the 
following  constitution  to  the  acid  : 

CH 


HC 
HC 


s\ 


CH— CO2H 


CH— C02H 


V 

CH 

1  Grabe  and  Born,  Ann.  Chem*  Pharm.  cxlii.  330. 
8  Baeyer,  Ber.  Deulsch.  Chem.  Ges.  xix.  1807. 

261 


470  AROMATIC  COMPOUNDS. 

Tetrahydrophthalic  acid,  C6H8(C02H)2.  The  anhydride  of  this 
acid,  C8H8O3,  is  formed  by  the  distillation  of  hydropyromellitic 
acid,  C6H6(C02H)4,  and  crystallizes  from  ether  in  hard,  lustrous 
plates,  which  melt  at  68°  and  sublime  readily.  It  is  insoluble  in 
cold  water,  but  dissolves  in  hot  water  with  formation  of  the  acid, 
which  crystallizes  in  large  plates,  and  is  readily  soluble  in  water, 
being,  however,  converted  into  the  anhydride  when  the  solution 
is  heated  to  about  1000.1 

Dibromotetrahydrophthalic  acid,  C6H6Br2(CO2H)2,  is  obtained 
by  the  combination  of  dry  bromine  with  dihydrophthalic  acid, 
and  crystallizes  in  rhombohedra  (Baeyer). 

HexhydropTithalic  acid,  C6H10(C02H)2,  is  formed  when  tetra- 
hydrophthalic acid  or  dihydrophthalic  acid 2  is  heated  to  230°  with 
hydriodic  acid,  or  when  the  former  is  treated  with  sodium  amalgam 
and  water,  while  dihydrophthalic  acid  is  not  attacked  by  these 
re-agents  (Baeyer).  It  is  slightly  soluble  in  cold,  somewhat  more 
readily  in  hot  water,  and  crystallizes  in  small  prisms  or  plates, 
which  melt  at  203° — 205°  without  forming  an  anhydride. 

Bromomaloplithalic  acid,  C6H8Br(OH)(C02H)2,  is  prepared  by 
adding  bromine  to  an  aqueous  solution  of  tetrahydrophthalic 
acid,  a  dibromide  being  first  formed,  which  is  then  decomposed 
by  water : 

C6H8Br2(C02H)2  +  H2O  =  C6H8Br(OH)(C02H)2  +  HBr. 

It  is  readily  soluble  in  water  and  crystallizes  in  small  rhombic 
prisms  or  tablets.  On  heating  with  baryta  water  it  is  converted 
into  the  following  compound.3 

Tartrophthalic  acid,  C6H8(OH)2(C02H)2  is  best  obtained  by 
dissolving  the  anhydride  of  tetrahydrophthalic  acid  in  boiling 
water,  and  adding  to  one  part  of  the  anhydride  rather  more  than 
an  equal  amount  of  bromine,  the  mixture  being  then  heated  on 
the  water  bath  and  treated  with  baryta  water  until  the  liquid 
has  a  permanent  alkaline  reaction.  The  barium  salt  is  obtained 
on  concentration  in  plates,  from  which  the  tartrophthalic  acid  is 
prepared  by  means  of  sulphuric  acid.  It  crystallizes  from  a  con- 
centrated solution  in  colourless  prisms  containing  two  molecules 
of  water,  which  are  lost  in  a  vacuum.  On  heating  with  hydri- 
odic acid  it  is  converted  into  hexhydrophthalic  acid,  the 

1  Baeyer,  Ann.  Chem.  Pharm.  clxvi.  344. 

2  Mierski,  Ber.  Deutsch.  Chem.  Ges.  iv.  558. 

3  Baeyer,  Ann.  Chem.  Pharm.  clxvl  354. 


CHLOROPHTHALIC  ACIDS.  471 

relation  existing  between  these  two  bodies  being  similar  to  that 
between  succinic  and  tartaric  acids,  while  tetrahydrophthalic 
acid  corresponds  to  fumaric  acid. 


HALOGEN  SUBSTITUTION  PRODUCTS  OF 
PHTHALIC  ACID. 

2246  Chlorine  does  not  act  upon  free  phthalic  acid,  even  in 
the  presence  of  iodine  ;  substitution  takes  place,  however,  when 
the  gas  is  passed  into  an  alkaline  solution  of  the  acid.  Auerbach 
obtained  in  this  way  a  monochlorophthalic  acid,  which  crystal- 
lized from -benzene  in  needles,  melted  at  149° — 150°,  was  readily 
soluble  in  alcohol  and  remained  on  the  evaporation  of  this  solu- 
tion as  a  syrup  which  gradually  solidified.  On  heating,  it  yielded 
an  anhydride  boiling  at  140° — 1430.1  Kriiger  obtained  different 
results  by  oxidizing  the  two  chloro-orthotoluic  acids  with  potas- 
sium permanganate  in  faintly  alkaline  solution.2 

v-Chlorophtkalic  acid,  C6H3C1(C02H)2(3  : 1  :  2),  is  also  formed 
by  the  oxidation  of  the  dichloronaphthalene  melting  at  107°,  and 
crystallizes  from  hot  water  in  stellate  groups  of  silky  needles, 
which  melt  at  184°  and  yield  an  anhydride  which  sublimes  in 
long  needles  and  melts  at  1*22° — 1230.3 

a-Chlorophthalic  acid  (4:1:2)  has  also  been  prepared  by  the 
oxidation  of  e-dichloronaphthalene  4  and  by  the  action  of  phos- 
phorus pentachloride  on  the  corresponding  sulphonic  acid.5  It 
is  more  readily  soluble  in  water  and  alcohol  than  the  v-acid, 
and  crystallizes  in  silky  needles,  which  melt  at  130° — 134° 
(Kriiger)  but  according  to  Olaus  and  Ree  at  148°.  It  decom- 
poses on  distillation  into  water  and  the  anhydride,  which 
crystallizes  in  lustrous,  asymmetric  tablets,  and  melts  at  96° — 97°. 

Dichlorophthalic  acid.  C6H2C12(CO2H)2,  is  obtained  by  heating 
dichloronaphthalene  tetrachloride,  C10C12H6C14,6  and  ^-dichloro- 
naphthalene 7  with  nitric  acid.  It  is  readily  soluble  in  alcohol 
and  hot  water,  and  crystallizes  in  compact  prisms,  which  melt  at 

1  Jahrcsb.  Chem.  1880,  862. 

2  Ber.  Deutsch.  Chem.  Ges.  xviii.  1758.  3  Gnareschi,  ibid.  xix.  134. 

4  Alen,  Bull.  Soc.  Chem.  xxxvi.  434  ;  Clans  and  Delme,  Ber.  Deutsch.  Chem. 
Ges.  xv.  319  ;  Claus  and  Miiller,  ibid,  xviii.  3073. 

5  R£e,  ibid,  xviii.  3359  ;  Inaugurate.  Bern.  1886. 

6  Faust,  Ann.  Chem.  Pharm.  clx.  64. 

7  Atterberg,  Ber.  Deutsch.  Chem.  Ges.  x.  574. 


472  AROMATIC  COMPOUNDS. 


183°— 185°.      Its  anhydride  melts  at   187°  and  forms  crystals 
which  are  very  similar  to  those  of  benzoic  acid. 

Trichlorophthalic  acid,  C6HC13(CO2H)2,  which  has  been  pre- 
pared by  the  oxidation  of  /?-pentachloronaphthalene  with  nitric 
acid,  forms  a  yellowish,  crystalline  mass,  and  is  converted  on 
heating  into  the  anhydride  which  melts  at  157°  and  sublimes 
in  long  needles.1 

Tetrachlorophthalic  acid,  CC14(CO2H)2.  was  -obtained  from 
a-pentachloronaphthalene.  It  is  also  formed  by  the  action  of 
chlorine  on  phthalic  acid  in  presence  of  antimony  chloride,2  and 
crystallizes  from  water  in  small  plates  or  hard,  thick  prisms, 
which  melt  at  250°  and  form  an  anhydride,  which  crystallizes  in 
long  needles,  melting  at  245°;  these  are  insoluble  in  cold 
water  but  gradually  dissolve  in  hot  water,  the  acid  being  re- 
formed.3 

Ethyl  tetrachlorophthalate,  C6C14(C02C2H6)2,  is  prepared  by 
heating  the  silver  salt  with  ethyl  iodide ;  it  forms  large  prisms 
which  melt  at  60°.  An  isomeric  compound  is  obtained  when 
the  acid  is  treated  with  phosphorus  chloride  and  the  tetrachloro- 
phthalyl  chloride  formed  submitted  to  the  action,  of  sodium 
ethylate  (p.  461) ;  it  crystallizes  in  tablets  and  melts  at  1240.4 

v-BromopUhalic  acid,  C6H3Br(C02H)2  (3:1: 2),  is  formed 
when  phthalic  acid  is  heated  with  bromine  and  water  to  180°; 
it  is  an  indistinctly  crystalline  powder  which  melts  at  138° — 140° 
and  yields  an  anhydride  melting  at  60° — 65°.5 

a-Bromophthalic  acid  (4  : 1  :  2)  is  obtained  by  the  oxidation  of 
bromonitronaphthalene,  C10H6Br(NO2),6  tetrabromo-/3-naphthol 7 
and  dibromamidonaphthalene 8    with  potassium  permanganate. 
It  crystallizes  in  white,  prismatic  needles,  which  melt  at  175°- 
176°  and  are  converted  into  an  anhydride  melting  at  131° — 132°. 

a-Dibromophthalic  acid,  C6H2Br2(C02H)2  (3:6:1: 2),  was  pre- 
pared by  Guareschi  by  the  oxidation  of  a-dibromonaphthalene 
with  nitric  acid.  It  separates  from  hot  water  as  a  crystalline 
powder,  which  melts  at  about  135°  with  decomposition;  on 
further  heating  the  anhydride  sublimes  in  light,  nacreous  needles 
melting  at  207'5°— 208°. 

1  Atterberg  and  Widmann,  Ber.  Deutsch.  Chem.  Ges.  x.  1843. 

"  Ibid,  xviii.  Kef.  676.  3  Grabe,  Ann.  Chem.  Pharm.  cxlix.  18. 

Grabe,  Ber.  Deutsch.  Chem.  Ges.  xvi.  860. 

Faust,  Ann.  Chem.  Pharm.  clx.  62  ;  Pechmann,  Ber.  Deutsch.  Chem.  Ges.  xii. 
2126. 

Guareschi,  Ann.  Chem.  Pharm.  ccxxii.  262. 

A.  J.  Smith.  Journ.  Chem.  Soc.  1879,  i.  792. 

Meldola,  ibid.  1885,  i.  511  ;  see  also  Stallard,  ibid.  1886,  i.  187. 


NITROPHTHALIC  ACIDS. 


473 


(S-Dibromophthalic  acid  is  formed  by  the  oxidation  of  penta- 
bromo-a-naphthol,  and  crystallizes  from  hot  water  in  needles 
which  melt  at  206°  and  are  thus  converted  into  the  anhydride, 
which  sublimes  in  long  needles  and  melts  at  208°.  The  salts  of 
this  acid  are,  with  the  exception  of  those  of  the  alkali  metals, 
only  slightly  soluble  in  water.1 

Tribromophthalic  acid,  C6HBr3(CO2H)2,  is  prepared  from  penta- 
bromo-/3-naphthol ;  it  is  almost  insoluble  in  cold  water  and 
crystallizes  from  hot  water  in  lustrous  plates  which  melt  at 
190° — 191°  and  are  converted  at  a  higher  temperature  into  the 
anhydride,  which  sublimes  in  white  plates  and  melts  at  1570.2 

Tetrdbromophthalic  acid,  C6Br4(CO2H)2,  was  obtained  by  Blum- 
lein  as  a  product  of  the  oxidation  of  tetrabromorthoxylene  ;  it  is 
almost  insoluble  in  the  ordinary  solvents,  and  crystallizes  from 
boiling  water  in  lustrous  needles,  and  on  the  evaporation  of  its 
solution  in  benzene  in  prisms,  which  melt  at  266°  and  are  thus 
converted  into  the  anhydride,  which  sublimes  in  small,  lustrous 
needles,  melting  at  258° — 259°.  Its  salts  are  for  the  most  part 
insoluble,  or  only  slightly  soluble,  in  water. 


NITROPHTHALIC  ACIDS. 

2247  v-NitropUhalic  acid,  C6H3(N02)(CO2H)2  (3:2: 1),  is 
formed  by  the  continued  boiling  of  naphthalene  with  nitric  acid,3 
by  the  action  of  a  mixture  of  nitric  and  sulphuric  acids  on  phthalic 
acid 4  and  by  the  oxidation  a-nitronaphthalene  with  potassium 
permanganate  5  or  of  a-dinitronaphthalene  with  nitric  acid.6  In 
order  to  prepare  it,  one  part  of  nitronaphthalene  is  dissolved  in 
7  parts  of  90  per  cent,  acetic  acid,  and  to  this  are  gradually  added 
5  parts  of  chromium  trioxide  ;  water  is  then  added  and  the  solu- 
tion extracted  with  chloroform  to  remove  the  orthonitrophthalide 
which  is  always  formed.  The  acid  liquid  is  then  treated  with 
barium  carbonate,  and  the  insoluble  barium  nitrophthalate  de- 
composed by  carbonate  of  soda.  The  solution  of  the  sodium 
salt  is  then  acidified  and  the  nitrophthalic  acid  extracted  with 

1  Bliimlein,  Ber.  Deutsch.  Chem.Ges.  xvii.  2485. 

2  Flessa,  ibid.  xvii.  1479. 

3  Laureut,  Ann.  Chcm.  Pharm.  xli.  110  ;  Marignac,  ibid.  xlii.  7. 

4  Faust,  ibid.  clx.  57. 

5  Guareschi,  Ber.  Deutsch.  Chem.  Ges.  x.  294. 

6  Aguiar,  ibid.  v.  899. 


474  AROMATIC  COMPOUNDS. 

ether.1  It  crystallizes  from  this  in  light  yellow,  monoclinic 
prisms,  which  are  slightly  soluble  in  cold,  more  freely  in  hot 
water,  and  readily  in  alcohol.  It  decomposes  on  heating  into 
water  and  the  anhydride ;  in  a  small  sealed  tube  it  melts  at  218° 
(Miller). 

Acid  ethyl  v-nitrophthalate,  C6H3(NO2)(C02C2H5)CO2H,  is  ob- 
tained by  passing  hydrochloric  acid  into  an  alcoholic  solution  of 
the  acid ;  it  crystallizes  from  hot  water  in  long  needles,  melting 
at  110-5°. 

Normal  ethyl  v-nitrophthalate,  C6H3(N02)(CO2C2H5)2,  is  pre- 
pared from  the  silver  salt  by  the  action  of  ethyl  iodide,  and 
crystallizes  from  alcohol  in  long,  rhombic  prisms,  melting  at  45° 
(Miller). 

a-Nitrophthalic  acid,  C6H3(NO2)(CO2H)2  +  H2O  (4:2:1),  is 
formed,  together  with  the  preceding  compound,  by  the  nitration 
of  phthalic  acid.2  In  order  to  prepare  it,  50  grms.  of  phthalic 
acid  are  heated  with  75  grms  of  sulphuric  acid  and  the  same 
amount  of  fuming  nitric  acid  for  two  hours  on  the  water  bath ; 
120  grms.  of  water  are  then  added,  and  the  whole  allowed  to 
stand  for  twelve  hours  in  the  cold.  The  precipitate  is  washed 
and  extracted  with  ether,  the  residue  after  the  evaporation  of 
this  consisting  of  a  mixture  of  the  two  acids  accompanied  by  a 
little  picric  acid.  It  is  re-crystallized  from  water,  to  remove  the 
greater  portion  of  the  v-acid,  the  mother  liquor  evaporated  to 
dryness,  and  the  residue  dissolved  in  alcohol  and  treated  with 
hydrochloric  acid  gas,  which  converts  the  v-acid  into  the  acid  and 
the  a-acid  into  the  normal  ether.  These  are  separated  by  car- 
bonate of  soda  solution,  and  the  normal  ether  then  converted 
into  the  potassium  salt  by  the  action  of  alcoholic  potash ;  this 
is  then  acidified  with  hydrochloric  acid  and  the  free  acid  ex- 
tracted with  ether.  It  may  be  still  more  easily  obtained  by 
heating  paranitrophthalide  with  dilute  nitric  acid  to  1400.3  It 
crystallizes  in  small  needles,  which  are  readily  soluble  in  water 
and  alcohol,  effloresce  in  the  air,  lose  their  water  at  100°,  and 
then  melt  at  161°. 

Acid  ethyl  a-nitrophthalate,  C6H3(NO2)(C02.C2H5)CO2H,  is 
formed  in  small  quantity  when  an  alcoholic  solution  of  the  acid 
is  treated  for  a  short  time  with  hydrochloric  acid,  and  crystallizes 
from  water,  in  long,  thin  needles,  which  melt  at  127° — 128°. 

1  Beilstein  and  Kurbatow,  Ann.  Chem.  Pharm.  ccii.  217. 

2  Miller,  ibid,  ccviii.  223. 

8  Honig,  Ber.  Deutsch.  Chem.  Ges.  xvii.  3447. 


AMIDOPHTHAL1C  ACIDS. 


475 


is  in- 


Normal ethyl  a-nitrophthalate,  C6H3(NO2)(C02.C2H£ 
soluble  in  water  and  crystallizes  from  alcohol  in  lustrous  tablets, 
which  melt  at  34°. 

a-Nitrophthalic  anhydride,  C8H3(NO2)O3,  is  obtained  by  heat- 
ing the  acid  to  170°  and  subliming  the  residue  in  a  current  of 
air  at  210°,  in  the  form  of  fascicular  crystals,  which  melt  at  114° 
and  are  readily  soluble  in  ether  and  hot  water.  If  the  aqueous 
solution  be  evaporated,  a-nitrophthalic  acid  is  deposited. 

Dinitrophthalic  acid,  C6H2(NO2)2(C02H)2  (5:3:2:1),  is 
formed  when  /8-dinitrophthalene  is  heated  to  150°  with  nitric 
acid  of  sp.  gr.  I'lo  in  a  sealed  tube,  small  quantities  of  nitro- 
phthalic  acid,  s-dinitrobenzoic  acid,  and  picric  acid  being  also 
formed.  It  crystallizes  in  large  prisms,  which  are  readily 
soluble  in  water  and  alcohol,  and  melt  at  2260.1 


XC02H 

AMIDOPHTHALIC    ACIDS,  C6H3^-NH2  . 

\C02H 

2248  v-Amidophthalic  acid.  When  the  v-nitro-acid  is  treated 
with  tin  and  hydrochloric  acid  in  the  cold,  needles  of  the  com- 
pound C6H3(NH2.ClH)(C02H)2-f-SnCl2+2H2O  are  formed.  If 
the  hydrochloric  acid  solution  of  this  be  treated  with  sulphuretted 
hydrogen  and  evaporated,  carbon  dioxide  is  given  off  and  meta- 
amidobenzoic  acid  formed. 

Ethyl  v-amidophthalate,  C6H3(NH2)(C02.C2H5)2,  is  prepared 
by  treating  a  well -cooled  alcoholic  solution  of  the  ether  of  the 
nitro-acid  with  hydrochloric  acid  and  zinc  dust.  It  is  a  yellow 
liquid,  which  decomposes  on  heating  and  forms  a  splendid  blue, 
fluorescent  solution  in  ether  (Miller). 

a-Amidophthalic  acid.  When  the  a-nitro-acid  is  reduced,  no 
carbon  dioxide  is  evolved,  but  no  double  tin  salt  is  formed.  On 
removing  the  tin  and  evaporating,  however,  carbon  dioxide  is 
evolved  just  as  in  the  case  of  the  v-acid,  and  metamidobenzoic 
acid  formed. 

If  the  reduction  be  carried  on  by  means  of  zinc  dust  and 

acetic  acid,  a  double  compound  of  zinc  acetate  and  zinc  amido- 

phenate  is  formed,  which  has  probably  the  constitution  C6H3 

(NH2)(C02H)CO2.Zn.O.CO.CH3,  and  crystallizes  in  fine,  white 

1  Beilstein  and  Kurbatow,  Ann.  Chem.  Pharm.  ccii.  224. 


476  AROMATIC  COMPOUNDS. 

needles,  which  form  an  almost  colourless  solution  in  hot  water, 
while  its  solution  in  acetic  acid  is  coloured  yellow  and  has  a 
green  fluorescence.  It  dissolves  in  caustic  soda,  but  the  solution 
decomposes  on  heating,  zinc  carbonate  is  deposited  and  the 
amidophthalic  acid  decomposed.1 

Ethyl  a-amidophthalate  was  first  prepared  by  Baeyer  but 
mistaken  for  the  v-compound 2  until  Miller  showed  that  it  is 
derived  from  the  a-acid.3  This  substance  is  obtained  in  a  similar 
manner  to  the  isomeric  compound;  it  is  insoluble  in  water, 
slightly  soluble  in  dilute  acid,  readily  in  alcohol,  from  which  it 
crystallizes  in  monoclinic  prisms,  which  melt  at  95° ;  the  dilute 
ethereal  solution  shows  a  faint  blue  fluorescence. 


H 
SULPHOPHTHALIC  ACIDS    aELSOJH. 

\C032H 

2249  a-Sulphophthalic  acid  (1:4:2)  is  obtained  by  heating 
phthalic  acid  or  phthalic  anhydride  with  strong,  fuming  sul- 
phuric acid,4  and  by  the  oxidation  of  /3-naphthalenesulphamide, 
C10H7S02.NH2,  and  dinitronaphtholsulphonic  acid,  C10H4(NO2)2 
(OH)S03H.5  It  remains  as  a  syrup  when  its  solution  is 
evaporated  on  the  water  bath,  but  solidifies  after  heating  for 
some  time  to  a  mass  consisting  of  stellate  groups  of  sharply 
pointed  prisms ;  these  contain  a  molecule  of  water,  which  is  lost 
at  140°,  a  brownish  syrup  being  formed,  which  often  solidifies 
on  standing.  On  heating  to  180°,  the  anhydride,  C6H3(C203) 
SO3H,  is  formed  as  a  hard,  brown,  very  hygroscopic  mass. 

The  normal  barium  salt  crystallizes  in  plates  or  silky  needles, 
slightly  soluble  in  water ;  when  it  is  dissolved  in  the  necessary 
amount  of  hydrochloric  acid,  the  monacid  salt,  C6H3(C02BaSO3) 
CO2H+2H20,  is  formed,  and  crystallizes  from  hot  water  in  large 
needles ;  it  is  converted  by  solution  in  an  excess  of  hydrochloric 
acid  into  the  diacid  salt,  (C6H3(CO2H)2SO3)2Ba+5H2O,  which 
also  crystallizes  in  lustrous  needles. 

1  Bernthsen  and  Semper,  Bcr.  Deutsch.  Chem.  Ges.  xix.  164. 

2  Ibid.  x.  124  and  1079. 
8  Ibid.  xi.  1191. 

4  Low,  Ann.  Chem.  Pharm.  cxliii.  249  ;  Ree,  Bcr.  Deutsch.  Chem.  Ges.  xviii. 
1629  ;  Inaugurald.  Bern.  1886  ;  Ann.  Chem.  Pharm.  ccxxxiii.  216. 
8  Grabe,  Ber.  Deutsch.  Chem.  Ges.  xviii.  1126. 


SULPHAMICPHTHALIC  ACIDS.  477 

When  the  monacid  ammonium  salt  is  heated,  the  ammonium 
salt  of  a-sulphophthalimide  is  formed  ;  it  crystallizes  in  mono- 
symmetric  prisms,  and  is  decomposed  on  heating  with  formation 
of  phthalimide  : 


>0  XC 

=  C6H4<    >0      +  S02  +  NH2  +  H20. 
S03NH4  XX) 

a-Sulphamidophthalic  acid,  C6H3(S03.NH2)(CO2H)2.  When 
a-sulphophthalic  anhydride  is  treated  with  phosphorus  penta- 
chloride,  the  monochloride,  C6H3(SO2C1)(CO2H)2,  is  formed,  and 
is  converted  by  ammonia  into  the  amide,  which  crystallizes 
from  water  in  small,  transparent  prisms  (Ree). 

v-Sulphophthalic  acid  (1:3:  2)  is  formed  when  a-naphthalene- 
sulphamide  is  oxidized  with  potassium  permanganate.  The  first 
product  is  the  anhydride  of  sulphamidophthalic  acid,  which 
yields  the  sulphonic  acid  on  heating  with  hydrochloric  acid  : 


V^gXi3— E5vJ2  -|-  ^  J.J-2VX    -^   VygJUJ-4  K_/V^3JL_I. 

\C02H  \CO2H 

It  is  readily  soluble  in  water,  and  forms  salts  which  crystallize 
well.1  The  normal  barium  salt,  (C6H3(CO2)2Ba.SO3)2Ba+8H2O, 
crystallizes  in  transparent  tablets. 

Sulphamidophthalic  anhydride  or  Sulphinidephthalic  acid, 
C8H5NS03+  2H20,  crystallizes  from  hot  water  in  needles,  which 
become  anhydrous  at  155.°  Alkalis  do  not  convert  it  into  sul- 
phamicphthalic  acid  ;  it  is  a  dibasic  acid,  the  hydrogen  of  the 
imide-group  being  easily  replaced  by  metals. 

Normal  potassium  sidphinidephthalate,  C8H3K2NSO3,  is  very 
readily  soluble  in  water  and  dries  to  an  elastic  mass,  from  which 
semi-crystalline,  spherical  masses  separate  on  standing. 

Acid  potassium  sulphinidephthalate,  C8H4KNS03  +  H2O,  is 
only  slightly  soluble  in  cold,  readily  in  hot  water,  and  crystallizes 
in  long  acute  prisms,  which  rapidly  lose  their  water  at  100°. 

Normal  silver  sulphinidephthalate,  C8H3Ag2NSO3  -f  H2O,  is  a 
white  precipitate,  which  is  scarcely  soluble  in  boiling  water,  but 
dissolves  in  a  hot  solution  of  potassium  nitrate  and  separates  out 
again  on  cooling. 

1  Remsen  and  Comstock,  Amer.  Chem.  Journ.  v.  106  ;  Stokes,  ibid.  \\.  262. 


478  AROMATIC  COMPOUNDS. 

Acid  silver  sulphinidephthalatc,  C8H4AgNSO3  -I-  H20,  is 
formed  when  the  normal  salt  is  heated  with  nitric  acid,  or  when 
silver  nitrate  is  added  to  a  dilute  boiling  solution  of  the  acid 
potassium  salt.  It  crystallizes  on  cooling  in  long,  pliant  needles, 
which  become  anhydrous  below  135°. 

The  silver  salt  is  converted  into  the  methyl  ether  by  treat- 
ment with  methyl  iodide. 

Normal  methyl  sulphinidcphthalate,  C8H3(CH3)2NS03,  crys- 
tallizes from  alcohol  in  colourless  needles,  which  melt  at  180°  and 
readily  sublime  in  iridescent  plates. 

Acid  methyl  sulphinidephthalate,  C8H4(CH3)NSO3,  separates 
from  an  alcoholic  or  hot  aqueous  solution  in  long,  striated  prisms, 
or  long,  narrow  tablets,  which  melt  at  1907°  —  191*7°  and  readily 
volatilize.  When  it  is  successively  treated  with  phosphorus 
trichloride  and  methyl  alcohol  the  dimethyl  ether  is  formed. 

In  order  to  determine  the  constitution  of  the  acid  sulphinide- 
phthalates,  the  acid  potassium  salt  was  heated  with  phosphorus 
pentachloride,  the  compound  C8H3C13S02NPOC12  being  formed  ; 
it  crystallizes  in  small  prisms,  and  is  converted  by  methyl  alcohol 
into  the  trimethyl  ether,  C8H4(CH3)3NSO6,  which  separates  from 
hot  water  in  needles  or  long  narrow  prisms,  which  melt  at  140'5°- 
141'5°.  The  constitution  of  these  compounds  is  expressed  by  the 
following  formulae  : 


2  •  632 

\COC1  \CO.OCH 


Since  the  monomethyl  ether  is  converted  into  the  diethyl  ether 
by  the  action  of  phosphorus  chloride  for  a  short  time,  followed  by 
the  treatment  described  above,  it  follows  that  in  the  first  of  these, 
and  therefore  in  the  acid  sulphinidephthalates,  it  is  the  hydrogen 
of  the  imido-group  which  is  replaced  (Stokes)  : 


3X Z  +    PC15  — 

\CO.OH 

>r ^^o  -}~  JbLOl-l-POC/Jq. 

\COC1 

-r  HO.CH3=C6H3^S02>NCHa  +HCL 
\COC1  \CO:OCH, 


ISOPHTHALIC  ACID.  479 


ISOPHTHALIC  ACID  OR  METAPHTHALIC  ACID. 

2250  This  compound  is  formed  by  the  oxidation  of  meta- 
xylene,1  metatoluic  acid,2  and  other  meta-compounds  with  two 
side-chains  containing  carbon.  It  has  also  been  obtained  by 
fusing  potassium  metasulphobenzoate 3  and  potassium  meta- 
bromobenzoate  *  with  sodium  formate  (Part  III.  p.  31),  and  has 
been  found  among  the  products  of  the  oxidation  of  colophony 
with  nitric  acid.5  In  order  to  prepare  it,  metaxylene  is  converted 
into  metaxylylene  diethyl  ether,  and  this  is  then  oxidized  with 
chromic  acid  solution,  the  reaction  proceeding  very  smoothly.6 
It  dissolves  in  7,800  parts  of  water  at  25°  and  in  460  parts  at 
100°,  crystallizing  in  hair-like  needles,  which  usually  extend 
through  the  whole  liquid,  and  are  readily  soluble  in  alcohol.7  It 
melts  at  above  300°  and  sublimes  without  decomposition. 

Potassium  isophthalate,  C8H4O4K2,  is  readily  soluble  in  water, 
less  readily  in  alcohol,  from  which  it  crystallizes  in  fascicular 
groups  of  needles. 

Calcium  isophthalate,  2C8H404Ca  +  5H2O,  is  scarcely  more 
soluble  in  hot  than  in  cold  water  and  forms  fine  needles. 

Barium  isophthalate,  2C8H4O4Ba  +  7H2O,  is  readily  soluble  in 
water  and  crystallizes  from  a  concentrated  solution  in  lustrous 
needles,  which  effloresce  in  the  air.8 

Silver  isophthalate,  C8H404Ag2,  is  an  amorphous  precipitate, 
which,  like  mercury  thiocyanate,  forms  a  voluminous  vermiform 
mass  on  heating. 

Methyl  isophthalate,  C8H4(CO2.CH3)2,  has  been  prepared  from 
the  silver  salt  by  means  of  methyl  iodide.  It  crystallizes  from 
dilute  alcohol  in  long  fine  needles,  melts  at  64° — 65°,  and  distils 
without  decomposition.9 

Ethyl  isophthalate,  C6H4(C02.C2H5)2,  has  been  obtained  by  the 
action  of  hydrochloric  acid  on  an  alcoholic  solution  of  the  acid. 

1  Fittig  and  Yelguth,  Ann.  Chem.  Pharm.  cxlviii.  11. 

2  Weith  and  Landolt,  Ber.  Deutsch.  Chem.  Ges.  viii.  721. 

3  V.  Meyer,  Ann.  Chem.  Pharm.  clvi.  275. 

4  Ador  and  Meyer,  ibid.  clix.  16. 

6  Fittig  and  Storss,  ibid,  cliii.  284. 

6  W.  H.  Perkin,  jun.  Private  communication. 

7  Fittig  and  Storss,  Ann.  Chem.  Pharm.  cliii.  284. 

8  Kelbe,  ibid.  ccx.  20. 

9  V.  Meyer,  Ber.  Deutsch.  Chem.   Ges.  iv.  262  ;  Baeyer,  Ann.  Chem.  Pharm. 
clxvi.  340. 


480  AROMATIC  COMPOUNDS. 

It  is  a  liquid  which  possesses  a  faint  but  pleasant  odour,  boils  at 
about  285°,  and  solidifies  at  0°  to  a  dazzling  white,  radiating  mass 
(Fittig  and  Storss). 

Phenyl  isophthalate,  C6H4(C02.C6H5)2,  is  formed  when  phenol 
is  heated  with  the  chloride  ;  it  crystallizes  in  long,  fine  needles 
which  melt  at  120°  and  are  only  slightly  soluble  in  alcohol.1 

Isophthalyl  chloride,  C6H4(COC1)2,  is  obtained  by  the  distilla- 
tion of  the  acid  with  phosphorus  chloride  as  an  oily  liquid,  which 
boils  at  276°  and  solidifies  to  a  radiating,  crystalline  mass,  melting 
at  41°  (Schreder). 

Isophtkalamidc,  C6H4(CO.NH2)2,  is  formed  by  the  action  of 
ammonia  on  the  chloride  and  is  a  light,  white  powder,  which 
melts  at  265°,  is  slightly  soluble  in  alcohol,  but  scarcely  dissolves 
in  any  other  of  the  ordinary  solvents.  On  heating  with 
phosphorus  pentoxide  it  is  converted  into  isophthalonitril.2 

Metacyanobenzoic  acid,  C6H4(CN)CO2H,  is  obtained  by  allow- 
ing a  hydrochloric  acid  solution  of  metadiazobenzoic  acid  to  run 
into  a  solution  of  copper  sulphate  and  cuprous  cyanide  : 


CN 
XCOH  XX)H 


2C6H4<  +  Cu2(CN)2  =  2C6H4  +  Cu2Cl2  +  2N2. 


2 

It  is  readily  soluble  in  alcohol  and  hot  water,  and  crystallizes 
from  the  latter  in  microscopic,  arborescent  needles,  which  after 
drying  form  a  dull  white  powder  and  melt  at  217°. 

Boiling  caustic  soda  solution  readily  converts  it  into  iso- 
phthalic  acid.3 

Ethyl  mctacyanobenzoate,  C6H4(CN)CO.C2H5,  crystallizes  in 
fine,  matted  needles,  which  melt  at  48°. 

Benzenylamidoximemetacarboxylic  acid,  is  prepared  by  heating 
metacyanobenzoic  acid  for  a  long  time  with  an  alcoholic  solution 
of  hydroxylamine,  and  forms  crystals  which  are  readily  soluble 
in  alcohol  and  hot  water,  and  melt  at  200°.  It  is  formed 
according  to  the  equation  : 

/ON 

C6H4<  2.  64 

\C02H  \C02H 

1  Schreder,  Bcr.  Deutsch.  Chem.  Gcs.  vii.  708. 

2  Beyer,  Journ.  Prakt.  Chem.  [2]  xxii.  351. 

8  Sandmeyer,  Ber.  Deutsch.  Chem.  Gcs.  xviii.  1496. 


CHLORO-ISOPHTHALIC  ACID.  481 

The  ethyl  ether  is  prepared  in  a  similar  manner  from  the 
corresponding  ether  of  metacyanobenzoic  acid  and  crystallizes 
from  hot  water  in  needles,  which  melt  at  1180.1 

Isophthalonitril,  C6H4(CN)2,  is  formed  by  the  distillation  of 
potassium  benzenemetadisulphonate  with  potassium  cyanide,2 
or  of  potassium  metabromosulphonate  with  dehydrated  potassium 
ferrocyanide ; 3  it  forms  fine  needles,  which  melt  at  160° — 161°, 
are  only  very  slightly  soluble  in  water,  somewhat  more  readily 
in  alcohol,  and  are  converted  into  isophthalic  acid  by  heating 
with  alkalis. 


ADDITION    PRODUCTS    OF   ISOPHTHALIC 
ACID. 

Tetrahydro-isophthalic  acid,  C6H8(G02H)2,  is  prepared  by  boil- 
ing an  alkaline  solution  of  isophthalic  acid  with  sodium  amalgam 
for  some  time,  and  crystallizes  from  hot  water  in  needles,  which 
melt  at  199°.  Its  dimethyl  ether  is  an  oily  liquid.4 


SUBSTITUTION    PRODUCTS    OF   ISOPHTHALIC 

ACID. 


2251  CUoro-isopUhalic  acid,  2C6H3C1(CO2H)2  +  H20,  has 
been  obtained  from  the  amido-acid  by  means  of  the  diazo- 
reaction,  and  crystallizes  from  hot  water  in  long,  very  fine 
needles,  which  become  anhydrous  at  120°,  and  melt  at  278° 
(Beyer). 

lodo-isopUhalic  acid,  C6H3I(C02H)2  (4:3:  1),  is  formed  by 
the  oxidation  of  acetyliodotoluene,  CH3.CO.C6H3I.CH3,  which 
will  be  subsequently  described.  It  is  scarcely  soluble  in  cold, 
only  very  slightly  in  boiling  water,  and  crystallizes  from  hot 
acetic  acid  in  small,  white  needles,  which  melt  at  203°  —  204°, 
but  sublime  in  white,  lustrous  flocks,  without  previously  melting, 
when  carefully  heated.  On  fusion  with  caustic  potash,  para- 

1  Miiller,  Bcr.  Deutsch.  Chem.  Ges.  xix.  1491. 

2  Earth  and  Senhofer,  ibid.  viii.  1481  ;  Ann.  Chem.  Pharm.  clxxiv.  235. 

3  Limpricht,  ibid,  clxxx.  92. 

4  Baeyer,  Bcr.  Devtsch.  Chem.  Ges.  xix.  1806. 


482  AKOMATIC  COMPOUNDS. 

hydroxybenzoic  acid  is  formed,  while  it  yields  benzoic  acid  when 
reduced  in  alcoholic  solution  by  sodium  amalgam.1 

Nitro-isophthalic  acid,  2C6H3(NO2)(CO2H)2  +  3H2O,  is  pre- 
pared by  heating  isophthalic  acid  with  fuming  nitric  acid  for 
some  time ; 2  it  is  slightly  soluble  in  cold,  very  readily  in  boiling 
water  and  alcohol,  and  crystallizes  in  thin,  lustrous  plates,  re- 
sembling those  of  benzoic  acid,  which  readily  lose  their  water 
and  melt  with  slight  decomposition  at  248° — 249°. 

Its  salts,  some  of  which  crystallize  well,  have  been  fully 
examined  by  Beyer. 

Methyl  nitro-isophthalate,  C6H3(N02)(CO2.CH3)2,  is  formed 
when  hydrochloric  acid  is  passed  into  an  alcoholic  solution  of 
the  acid,  and  crystallizes  in  fine,  lustrous  needles,  which  melt  at 
121 '5°,  and  yield  a  vapour  which  smells  like  aniseed. 

Ethyl  nitro-isophthalate,  C6H3(N02)(CO2.C2H5)2,  forms  fine 
needles  or  transparent  prisms,  which  melt  at  83"  5°. 

Amido-isophthalic  acid,  C6H3(NH2)(CO2H)2,  is  readily  obtained 
from  the  nitro-acid  by  reduction  with  tin  and  hydrochloric  acid. 
It  is  only  slightly  soluble  in  cold  water  and  alcohol,  crystallizing 
from  hot  water  in  lustrous  plates  and  from  alcohol  in  prisms. 
It  combines  with  acids  and  bases  forming  compounds  which 
have  been  investigated  by  Beyer.  Its  ethers  are  obtained  by 
the  reduction  of  the  corresponding  nitro-compounds. 

Methyl  amido-isophthalate,  C6H3(NH2)(CO2.CH3)2,  crystallizes 
from  wood-spirit  in  thin,  yellowish  plates  or  tablets,  which  melt 
at  176> 

Ethyl  amido-isophthalate,  C6H3(NH2)(C02.C2H5)2,  forms  thin 
plates  or  fascicular  needles,  melting  at  118°.  Its  ethereal 
solution  has  a  splendid  violet  fluorescence. 

s-Sulpho-isophthalic  acid,  CH3(C02H)2SO3H  +  2H20  (1:3: 5), 
is  prepared  by  the  action  of  sulphur  trioxide  on  isophthalic  acid,3 
and  by  heating  the  latter  to  200°  with  fuming  sulphuric  acid.4 
It  is  very  readily  soluble  in  water,  but  only  slightly  in  dilute 
sulphuric  acid,  and  crystallizes  in  long  needles  or  transparent, 
four-sided,  pointed,  rhombic  columns,  which  effloresce  in  dry 
air,  but  deliquesce  in  very  damp  air.  The  anhydrous  acid  melts 
at  257° — 258°,  a  slight  discolouration  taking  place. 

a-Sulpho-isophthalicacid,  C6H3(CO2H)2SO3H  +  2H2O  (1:3:  4), 
is  obtained  by  the  oxidation  of  an  alkaline  solution  of  a-meta- 

1  Klingel,  Ber.  Deutsch.  Chem.  Ges.  xviii.  2701. 

2  Fittig  and  Storss,  ibid,  cliii.  285  ;  Beyer,  Journ.  Prakt.  Chcm.  [2]  xxv.  465. 
8  Heine,  Ber.  Deutsch.  Chem.  Ges.  xiii.  491.          4*Lonnies,  ibid.  xiii.  703. 


TEREPHTHALIC  ACID.  483 

xylenesulphonic  acid,1  or  metatoluylsulphamic  acid  2  with  potas- 
sium permanganate.  It  is  readily  soluble  in  water,  and  crystallizes 
from  dilute  sulphuric  acid  in  flat,  very  hygroscopic  needles 
melting  at  235°— 240°. 


TEREPHTHALIC   ACID. 

2252  Paraphthalic  acid  is  readily  formed  by  the  oxidation  of 
those  para-  compounds  which  possess  two  side-chains  containing 
carbon,  such  as  paraxylene,3  cymene,  or  methylpropylbenzene, 
CH3.C6H4.C3H7,  cuminol  or  cuminaldehyde,  COH.C6H4.C3H7,4 
paratoluic  acid,5  &c.  Caillot,  as  already  mentioned,  obtained  it 
from  oil  of  turpentine,  C10H16,  which  is  closely  related  to  cymene. 
The  isomerides  of  this,  oil  of  cajeput,  oil  of  citron,  and  the 
thymene  contained  in  thymian,  all  yield  terephthalic  acid  on 
oxidation,6  and  it  is  also  formed  when  potassium  parasulpho- 
benzoate  is  fused  with  sodium  formate.7 

In  order  to  prepare  it,  a  mixture  of  100  grms.  of  paraxylene, 
which  need  not  be  pure,  400  grms.  of  potassium  dichromate  and 
550  grms.  of  sulphuric  acid,  diluted  with  two  volumes  of  water, 
is  heated  for  several  days  in  a  flask  connected  with  a  reflux 
condenser  until  the  solution  has  become  coloured  a  pure  green  ; 
the  unattacked  xylene  is  then  distilled  off,  and  the  solution 
filtered  from  the  precipitated  acid,  which  is  dissolved  in  dilute 
carbonate  of  soda  and  precipitated  by  hydrochloric  acid.  The 
acid  is  obtained  pure  by  repeating  this  process  two  or  three 
times. 

Cymene,  which  is  easily  prepared  by  distilling  camphor  with 
phosphorus  pentoxide,  may  be  employed  instead  of  paraxylene, 
or  Roman  cumin  oil,  a  mixture  of  cymene  and  cuminol,  may 
be  used. 

Terephthalic  acid  is  a  tasteless  powder,  which  appears  crystal- 
line under  the  microscope,  is  insoluble  in  ether  and  chloroform, 
and  scarcely  soluble  in  water  and  alcohol  ;  the  hot,  saturated, 
aqueous  solution  has  an  acid  reaction,  and  deposits  the  acid  on 

1  Jacobsen  and  Lonnies,  Ber.  Deutsch.  CUem.Ges.  xiii.  1556. 

-  Coale  and  Remsen,  Amer.  Chem.  Journ.  iii.  214. 

3  Bcilstein,  Ann.  Chem.  Pharm.  cxxxiii.  40. 

4  Miiller  and  Warren  de  la  Rue,  ibid.  cxxi.  87. 

5  Beilstcin  and  Yssel  de  Schepper,  ibid,  cxxxvii.  308. 

6  Schwanert,  ibid,  cxxxii.  260. 

7  Remsen,  Ber.  Deutsch.  Chem.  Ges.  v.  379. 


484  AROMATIC  COMPOUNDS. 

cooling  as  an  indistinctly  crystalline  powder.  It  sublimes  when 
heated  without  previously  melting. 

Ammonium  terephthalate,  C8H4O4(NH4)2,  is  deposited  on  the 
evaporation  of  its  solution  in  small,  lustrous  crystals. 

Calcium  terephthalate,  C8H4O4Ca  +  3H20,  separates  from  hot 
water  in  small  crystals,  which  dissolve  in  1,214  parts  of  water 
at  6°. 

Barium  terephthalate,  C8H4O4Ba  +  4H20,  is  deposited  from  a 
rapidly  cooled  solution  as  a  white,  granular  powder ;  by  gradual 
evaporation  it  is  obtained  in  small,  concentrically  arranged  tablets, 
which  dissolve  in  355  parts  of  water  at  5°. 

Silver  terephthalate,  C8H404Ag2,  is  an  amorphous  precipitate, 
which  blackens  in  the  light. 

Methyl  terephthalate,  C8H4O4(CH3)2, 4s  formed  by  the  action  of 
the  chloride  on  methyl  alcohol,1  and  crystallizes  from  hot  alcohol 
in  large  flat  prisms,  which  melt  at  140°  and  are  volatile  without 
decomposition.  By  means  of  this  compound  the  smallest  quantity 
of  terephthalic  acid  can  be  detected.  The  substance  is  treated 
with  phosphorus  chloride  and  then  with  methyl  alcohol,  water 
being  finally  added  and  the  methyl  compound  extracted  with 
ether.  On  the  evaporation  of  the  latter  characteristic  crystals 
of  the  compound  are  obtained. 

Ethyl  terephthalate,  C6H4(C02.C2H5)2,  forms  white  odourless 
prisms,  which  resemble  those  of  urea  and  melt  at  44°. 

The  following  ethereal  salts  have  been  prepared  by  Beyer, 
some  by  means  of  the  chloride,  the  remainder  from  the  silver 

salt:2 

Melting- 
point. 

Propyl  terephthalate,  C6H4(C02.C3H7)2,  long  needles  ....  31'0° 
Isopropyl  terephthalate,  C6H4(CO2.C3H7)2,  lustrous  plates  .  55'5° 
Isobutyl  terephthalate,  C6H4(C02.C4H9)2~ needles 52'5° 

The  normal  butyl  ether  is  liquid,  while  the  tertiary  butyl 
ether  is  only  formed  with  great  difficulty,  and  has  not  yet  been 
obtained  in  considerable  amount.  Miiller  and  Warren  de  la 
Rue  have  prepared  the  amyl  ether;  it  crystallizes  in  scales, 
which  are  melted  even  by  the  warmth  of  the  hand. 

Phenyl  terephthalate,  C6H4(CO2.C6H5)2,  crystallizes  from  alcohol 
in  fine  needles,  melting  at  19 10.3 

1  Warren  de  la  Rue  and  Muller  ;  Schwanert,  loc.  cit. 

2  Ber.  Deutsch.  Chem.  Ges.  x.  1742. 

3  Schreder,  ibid.  vii.  707. 


TEREPHTHALAMIC  ACID. 


485 


TerepUhalyl  chloride,  C6H4(COC1.)2,  is  formed  by  the  distilla- 
tion of  the  acid  with  phosphorus  pentachloride  and  is  a  crys- 
talline mass,  which  has  a  somewhat  sharp  odour  resembling 
cinnamon,  melts  at  78°  (Schreder)  and  boils  at  259°  (Beyer). 

Terephthalamide,  C6H4(CO.NH2)2,  is  obtained  by  the  action 
of  ammonia  on  the  chloride,  as  a  white  amorphous  powder, 
which  is  insoluble  in  all  solvents  (Warren  de  la  Rue  and 
Muller). 

Terephthalamic  acid,  C6H4(CO.NH2)C02H,  is  obtained  as  the 
product  of  all  reactions  by  which  paracyanobenzoic  acid  might  be 
prepared,  as  the  elements  of  water  are  taken  up  by  the  latter 
according  to  the  following  equation  : 


,CN 


=  C6H4< 


Terephthalamic  acid  crystallizes  in  indistinct,  microscopic 
plates,  which  are  slightly  soluble  in  cold,  readily  in  hot  water 
and  alcohol,  melt  at  214°,  and  are  converted  into  terephthalic 
acid  by  boiling  with  caustic  soda  (Sandmeyer). 

Ethyl  paracyanobenzoate,  C6H4(CN)CO2.C2H5,  is  prepared  from 
ethyl  paramidobenzoate  and  crystallizes  in  needles,  melting  at 
54°.  On  heating  with  an  alcoholic  solution  of  hydroxylamine, 
the  ethyl  ether  of  benzenylamidoximeparacarboxylic  acid,  C6H4 
(CO2H)C(NH2)NOH,  is  formed  ;  it  melts  at  135°  and  yields  the 
free  acid  which  melts  above  330°. l  The  meta-  and  para-cyano- 
benzoic  acids  and  their  ethers,  therefore,  behave  towards  hydro- 
xylamine like  other  nitrils,  while  the  ortho-compounds  differ 
from  these. 

Terephthalonitril,  C6H4(CN)2,  is  prepared  by  heating  terephtha- 
lamide  with  phosphorus  pentoxide  (Warren  de  la  Rue  and 
Muller)  or  by  distilling  potassium  benzeneparadisulphonate,2 
potassium  parachlorobenzenesulphonate,3  or  potassium  para- 
bromobenzenesulphonate  4  with  potassium  cyanide  or  dehydrated 
potassium  ferrocyanide.5  It  is  insoluble  in  water,  slightly  soluble 
in  cold,  readily  in  hot  alcohol,  and  crystallizes  in  needles  or 
lustrous  prisms,  which  melt  at  215°  and  readily  sublime.  It  is 

1  Miiller,  Bcr.  Deutsch.  Chem.  Gcs.  xviii.  2485  ;  xix.  1491. 

2  Garrick,  Zcitschr.  Chem.  IS 69,  551. 

3  Nolting,  Bcr.  Deutech.  Chan,.  Gcs.  viii.  1110. 

*  Irelan,  Zcitschr.  Chem.  1869,  164  ;  Earth  and  Senliofer,  Ann.  Chem.  PJiarm. 
174,  242. 

3  Limpriclit,  ibid,  clxxx.  88. 

262 


486  AROMATIC  COMPOUNDS. 

converted  into  terephthalic  acid  by  boiling  with  an  aqueous,  or 
more  rapidly  with  an  alcoholic,  solution  of  potash.  It  is,  how- 
ever, better  to  decompose  it  by  heating  to  160°  with  hydrochloric 
acid  (Limpricht). 


ADDITION  PRODUCTS  OF  TEREPHTHALIC 
ACID.i 

2253  Tetrahydroterephthalic  acid,  C6H8(CO2H)2.  In  order  to 
prepare  this  substance,  5  grins,  of  terephthalic  acid  are  dissolved 
in  a  little  caustic  soda  solution  and  boiled  for  twenty  hours,  500 
grms.  of  4  per  cent,  sodium  amalgam  being  gradually  added. 

It  is  scarcely  soluble  in  cold  water  and  requires  120  parts  of 
boiling  water  for  solution,  from  which  it  crystallizes  on  cooling 
in  small,  arborescent  prisms,  which  melt  above  300°  and  sublime. 
Its  silver  salt  is  a  white  amorphous  precipitate  which  blackens  in 
the  light. 

Methyl  tetrahydroterephthalate,.  C6H8(CO2.CH3)2,  is  formed  by 
the  action  of  methyl  iodide  on  the  silver  salt,  as  well  as  by 
passing  hydrochloric  acid  into  a  solution  of  the  acid  in  wood- 
spirit.  It  is  thus  obtained  as  an  oily  liquid,  which  smells  of 
fennel  and  soon  solidifies  in  large  prisms,  melting  at  39°.  It 
crystallizes  from  ether,  in  which  it  forms  a  blue  fluorescent 
solution,  in  long  needles. 

Hexhydroterephthalic  acid,  C6H10(CO2H)2,is  obtained  by  heating 
the  tetrahydro-acid  to  240°  for  six  hours  with  concentrated 
hydriodic  acid.  It  is  even  less  soluble  in  water  than  the  tetra- 
hydro-compound  and  crystallizes  from  hot  water  in  small  prisms, 
melting  at  about  295°.  It  is  very  stable  towards  alkaline  per- 
manganate solution,  while  the  tetrahydro-derivative  is  oxidized 
to  oxalic  acid  by  this  even  in  the  cold.  Its  methyl  ether  melts 
at  58°  and  resembles  the  preceding  compound,  but  does  not 
give  a  fluorescent  solution. 

Dibromohexhydroterephthalic  acid,  C6H8Br2(C02H)2  -f  H20, 
is  best  prepared  by  treating  finely  divided  tetrahydroterephthalic 
acid  for  several  hours  with  an  ethereal  solution  of  bromine,  the 
mixture  being  agitated  at  intervals,  and  repeating  this  operation 
until  the  acid  is  almost  completely  dissolved.  The  solution  is 

J  Baeyer,  Bcr.  Deutsch.  Chcm.  Ges.  xix.  1805. 


TETRAHYDROTEREPHTHALIC  ACID.  487 

then  decolourized  with  sulphur  dioxide  and  the  acid  extracted 
by  carbonate  of  soda  solution.  It  is  precipitated  from  the  latter 
by  hydrochloric  acid  in  granular,  cubic  crystals.  Its  methyl  ether 
is  formed  by  the  combination  of  bromine  with  the  ether  of 
tetrahydroterephthalic  acid,  and  crystallizes  in  large  prisms 
melting  at  73°. 

Tetrahydrophthalic  acid  behaves  towards  bromine  in  the  same 
manner  as  cinnamic  and  fumaric  acids.  When  the  brominated 
acid  is  heated  with  caustic  soda  solution,  a  dihydroterephthalic 
acid  is  formed,  which  resembles  terephthalic  acid  very  closely. 
A  syrupy  acid  is  however  formed  by  the  action  of  freshly  pre- 
cipitated silver  oxide,  which  is  probably  a  dihydroxyhexhydro- 
terephthalic  acid,  and  is  converted  by  the  action  of  bromine  into 
tetrabromocatechol  : 

C6H8(OH)2(C02H)2  +  7Br2  =  C6Br,(OH)2  +  2C02  +  1  OHBr. 

The  constitution  of  tetrahydrophthalic  acid  is  proved  by  the 
formation  of  this  substance,  and  may  also  be  deduced  from  the 
following  considerations. 

Phthalic  acid  only  assumes  two  atoms  of  hydrogen  when  acted 
upon  by  sodium  amalgam  and  water,  while  isophthalic  and  tere- 
phthalic acids  combine  with  four.  The  simplest  explanation  of 
this  fact  is  that  the  double  linking  of  two  carbon  atoms  is  con- 
verted into  a  single  one,  if  at  least  one  of  these  be  combined  with 
a  carboxyl  group.  The  following  formulae  are  thus  arrived  at  : 

Dihydrophthalic  acid.  Tetrahydro-isophthalic  acid. 

CH  CH—  C02H 

HC^  \CH—  C02H  H2Cj/\CH2 

Hc'\/CH—  CO9H  HC\/CH—  C02H 

CH  CH 

Tetrahydroterephthalic  acid.  Dihydroxyhexhydroterephthalic  acid. 

CH—  CO2H  CH—  C02H 


H2C\/CH  H2C\/CH.OH 

CH—  CO2H  CH—  C02H 


488  AROMATIC  COMPOUNDS. 


SUBSTITUTION  PRODUCTS   OF    TERE- 
PHTHALIC   ACID. 

2254  Chloroterephthalic  acid,  C6H3C1(CO2H),  is  prepared  from 
amidoterephthalic  acid,  and  is  slightly  soluble  in  hot  water,  more 
readily  in  alcohol.  It  is  crystalline,  and  melts  above  300°.  The 
chloride,  C6H3C1(COC1)2,  obtained  by  the  action  of  phosphorus 
chloride,  is  also  crystalline  and  boils  at  about  300°.  By  treating 
this  with  ammonium  carbonate,  the  arnide,  C6H3C1(CO.NH2)2, 
is  formed,  and  crystallizes  from  alcohol  in  crusts,  melting  above 
300°. 

Methyl  chloroterephthalate,  C6H3C1(C02.CH3)2,  forms  silky 
plates,  melting  at  60.° 1 

Bromoterephthalic  acid,  C6H3Br(CO2H)2  +  H2O,  is  formed  by 
the  action  of  potassium  permanganate  on  an  alkaline  solution 
of  bromoparatoluic  acid.  ,  It  is  almost  insoluble  in  cold  water, 
and  crystallizes  from  hot  water  in  dazzling  white,  microscopic 
needles,  which  melt  at  304° — 305°.  Phosphorus  pentachloride 
converts  it  into  the  chloride,  C6H3Br(COCl)2,  an  oily  liquid, 
which  boils  at  3 04' 5° — 305 '5°,  is  only  gradually  decomposed  by 
water,  and  combines  with  aqueous  ammonia  to  form  the  amide, 
C6H3Br(CO.NH2)2,  which  crystallizes  from  hot  water  in  small 
needles,  melting  at  270°. 

Methyl  lrow,oterephthalate,  C6H3Br(C02.CH3)2,  crystallizes  in 
concentrically  arranged  groups  of  needles,  melts  at  42°  and  boils 
at  above  3000.2 

Dibromoterephthalic  acid,  C6H2Br2(C02H)2,  is  prepared  by  heat- 
ing dibromocymene,  C6H2Br2(CH3)C3H7,  for  some  time  with 
nitric  acid,3  and  by  the  oxidation  of  dibromotoluic  acid  with 
potassium  permanganate.4  It  crystallizes  from  hot,  dilute  alcohol 
in  small  plates,  which  have  a  satin  lustre,  do  not  melt  even  at 
320°,  and  sublime  at  a  higher  temperature  with  decomposition. 

Ethyl  dibromoterephthalate  crystallizes  from  alcohol  in  nacreous 
plates,  melts  at  121°  and  boils  at  about  335°. 

Nitroterephthalic  acid,  C6H3(NO2)(C02H)2,  is  formed  by  treat- 
ing terephthalic  acid  with  a  mixture  of  fuming  sulphuric  and 

1  Ahrens,  Ber.   Deutsch.   Chem.   Ges.  xix.  1634. 

2  Fischli,  ibid.  xii.  619. 

3  Claus  and  Wimmel,  ibid.  xiii.  902. 

4  Schultz,  ibid,  xviii.  1762. 


CHLOROTEREPHTHALIC  ACID.  489 

nitric  acids,  and  crystallizes  in  prisms  ;  it  separates  from  hot 
water  in  cauliflower-like  masses,  which  melt  at  2700.1 

Methyl  nitrotcrcphthalate,  C6H^NO2)(CO2.CH3)2,  crystallizes 
from  ether  in  splendid  prisms,  which  melt  at  70°.2 

Nitroterephthalamide,  C6H3(NO2)(CO.NH2)2,  was  obtained  by 
Warren  de  la  Rue  and  Miiller  in  well  formed  prisms  by  the 
nitration  of  terephthalamide. 

Amidoterephthalic  acid,  C6H3(NH2)(CO2H)2,  is  formed  by  the 
reduction  of  the  nitro-acid  with  tin  and  hydrochloric  acid,  and 
crystallizes  in  thin,  lemon-yellow  prisms  or  moss-like  forms, 
which  are  only  slightly  soluble  in  cold  water  and  alcohol,  and 
decompose  on  heating  without  melting.  Their  aqueous  or 
alkaline  solutions,  and  those  of  their  salts  and  ethers,  which 
latter  are  crystalline  bodies  but  have  not  been  described  in 
detail,  show  a  remarkable  blue  fluorescence,  while  acidified 
solutions  of  the  acid  do  not  possess  this  property. 

Methyl  am^o^r^A^a/a^,C6H3(NH2)(CO2CH3)2,  forms  crystals, 
melting  at  126°;  its  alcoholic  and  ethereal  solutions  also  show  a 
strong  blue  fluorescence  (Ahrens). 

Diamidoterephthalic  acid,  C6H2(NH2)2(CO2H)2,  is  not  known 
in  the  free  state;  its  ethyl  ether  has  been  prepared  from 
succinosuccinic  ether  (Pt.  III.,  p.  146).  When  the  latter  is 
heated  with  ammonium  acetate,  a  di-imide  is  formed,  which 
crystallizes  in  shining,  yellow  needles,  melting  at  181°.  Diethyl- 
diamidoterephthalate  is  obtained  by  the  action  of  bromine  on  its 
solution  in  sulphuric  acid  : 

CO.CH5  CO2.C2H6 


CH  0 


+  Br2=xl2^ 

H2C\/C=NH 
CH 

C02C2H5  C02C2H6 

It  crystallizes  from  hot  alcohol  in  lustrous  golden  needles  of 
the  colour  of  potassium  dichromate,  which  melt  at  168°.  Its 
brown  alcoholic  or  ethereal  solution  shows  a  golden-yellow 
fluorescence.  It  forms  slightly  soluble  salts  with  hydrochloric 
and  sulphuric  acids. 

1  Warren  de  la  Rue  and  M  filler,  Ann.  Chem.  Pharm.  cxxi.   90  ;  Burckhardt, 
Ber.  Deutsch.  Chem.  Gcs.  x.  144.  2  Ahrens,  ibid.  xix.  1634. 


490  AROMATIC  COMPOUNDS. 

When  a  solution  of  its  diazo-compound  in  hydrochloric  acid  is 
heated  with  an  acid  solution  of  cuprous  chloride,  an  acid  is 
formed  which  is  probably  dichloroterephthalic  acid,  since  it  is 
converted  into  terephthalic  acid  by  the  action  of  sodium  amalgam 
and  water.1 

Sulphoterephtlialic  acid,  C6H3(S03H)(CO2H)2,  is  obtained  by 
heating  terephthalic  acid  with  fuming  sulphuric  acid,2  and  by 
the  oxidation  of  sulphoparatoluic  acid,  paratoluylsulphamic  acid, 
or  paraxylenesulphonic  acid  with  potassium  permanganate.3  It 
forms  a  hygroscopic  mass,  and  yields  salts  which  are  soluble  in 
water,  but  insoluble  in  alcohol. 


HYDROXYMETHYLHYDROXYBENZOIC  ACID, 

/OH 

C6H3fCG2H 
\CH2.OH. 

2255  These  compounds,  which  are  simultaneously  alcohols  and 
phenols,  are  formed  by  the  action  of  sodium  amalgam  on  the 
aldehydo-acids,  which  are  described  below.4 

Orthohydroxymelhylsalicylic  acid  (1:2:  6)  is  precipitated  by 
acids  from  its  alkaline  solution  as  an  oil,  which  solidifies  after 
some  time  to  hard,  white  crystals ;  it  is  readily  soluble  in  hot 
water,  alcohol  and  ether,  and  crystallizes  from  the  latter  in 
transparent  prisms,  which  melt  at  142°.  Its  aqueous  solution 
is  coloured  an  intense  bluish-violet  by  ferric  chloride. 

Parahydroxymethylsalicylic  acid  (1:2:4)  is  slightly  soluble 
in  alcohol  and  ether,  and  crystallizes  from  the  latter  in  long 
prisms,  which  melt  at  160°  with  decomposition.  Ferric  chloride 
colours  the  solution  violet. 

Orthohydroxymelhylparaliydroxybenzoic  acid  (1:4:2)  is  a 
white  powder,  which  does  not  melt  below  270°,  and  gives  no 
colouration  with  ferric  chloride. 

1  Baeyer,  Ber.  Deutsch.  Chem.  Gcs.  xix.  428. 

2  Ascher,  Ann.  Chem.  Pharm.  clxi.  2  ;  Schoop,  Ber.  Deutsch.  Chem.  Ges.  xiv. 
223. 

3  Hall  and  Remsen,  ibid.  xii.  1434 ;  Burney  and  Remsen,  Amer.  Chem.  Journ. 
ii.  405  and  413. 

4  Reimer,  Ber.  Deutsch.  Chem.  Ges.  xi.  790. 


ALDEHYDOHYDKOXYBENZOIC  ACIDS.  491 


ALDEHYDOHYDROXYBENZOIC     ACIDS, 

/OH 

C6H/C02H 
\COH 

2256  These  are  prepared  by  heating  the  hydroxybenzoic  acids 
with  caustic  soda  and  chloroform : 


C6H4<  4  SNaOH  4  CHC13  = 

Ta 

/ONa 


w  +3NaCl42H20. 

\C02Na 

They  are  converted  by  reduction  into  the  preceding  alcohol- 
acids,  and  by  fusion  with  caustic  potash  into  the  hydroxyphthalic 
acids.  They  combine,  like  other  aldehydes,  with  the  sulphites  of 
the  alkali  metals. 

Ortho-aldchydosalicylic  acid  (1  :  2  :  6)  is  obtained,  together 
with  the  following  compound,  from  salicylic  acid.  It  crystallizes 
in  fine,  matted  needles,  which  dissolve  at  23° — 25°  in  1,500— 
1,600  parts,  or  at  100°  in  15—16  parts  of  water.  The  aqueous 
solution  is  coloured  deep  yellow  by  caustic  soda,  and  red  by 
ferric  chloride,  and  the  alcoholic  solution  shows  a  faint,  bluish 
violet  fluorescence.  It  melts  at  179°  and  sublimes  without 
decomposition  when  carefully  heated.  On  distillation  with 
slaked  lime  it  decomposes  into  salicylaldehyde  and  carbon 
dioxide.  The  copper  salt  is  a  gelatinous  precipitate,  which 
is  soluble  in  ammonia;  on  boiling  the  solution  a  light  blue 
precipitate  of  C8H4O4Cu  is  thrown  down. 

Para-aldehydosalicylic  acid  (1:2:4)  forms  long,  fine  needles, 
which  melt  at  248°— 249°,  and  dissolve  in  2,600—2,700  parts  of 
water  at  25°,  and  in  145 — 150  parts  at  100°.  Its  aqueous 
solution  is  not  coloured  by  caustic  soda,  while  ferric  chloride 
produces  a  deep  cherry-red  colouration.  On  distillation  with 
lime,  parahydroxybenzaldehyde  is  formed;  its  copper  salt  is 
also  soluble  in  ammonia,  but  is  not  precipitated  on  boiling.1 

Ortho-aldehydoparahydroxylenzoic  acid  (1:4:2),  was  obtained 
by  Reimer  and  Tiemann  from  parahydroxybenzoic  acid;  it 
1  Reimer  and  Tiemann,  Bcr.  Deutsch.  Chem.  Ges.  ix.  1268,  x.  1562. 


492  AROMATIC  COMPOUNDS. 

crystallizes  from  hot  water  in  thin,  arborescent  prisms,  which 
melt  at  243° — 244°,  and  sublime  in  splendid,  white  needles. 
Its  aqueous  solution  is  coloured  deep  yellow  by  caustic  soda  and 
brownish  red  by  ferric  chloride.  Salicylaldehyde  is  formed  when 
it  is  distilled  with  caustic  lime. 

Ortho-aldehydometahydroxybenzoic  acid  (1:3:6)  is  obtained, 
together  with  the  following  compound,  from  metahydroxybenzoic 
acid.  It  crystallizes  in  needles,  which  melt  at  234°,  and  are 
slightly  soluble  in  hot  water  and  readily  in  alcohol.  Its  aqueous 
solution  is  coloured  violet  by  ferric  chloride  and  deep  yellow  by 
caustic  soda.  On  boiling  with  caustic  soda  it  is  only  decomposed 
at  a  high  temperature,  phenol  being  formed. 

Para-aldehydometahydroxylenzoic  acid  (1:3:4)  has  only  been 
obtained  as  a  syrup ;  it  is  very  unstable  and  reduces  Fehling's 
solution  readily.  On  fusion  with  caustic  potash  it  is  converted 
into  a-hydroxyisophthalic  acid.1 


>H 
HYDROXYPHTHALIC  ACIDS,  CBH-f-< 


2H 

2257  a-Hydroxyphthalic  acid  (4:1:  2).  When  the  ethyl  ether 
of  a-amidophthalic  acid  is  dissolved  in  dilute  sulphuric  acid, 
treated  with  sodium  nitrite  and  then  heated  to  100°,  the  ether 
of  a-hydroxyphthalic  acid  separates  out  as  a  yellowish  oil,  which 
yields  the  free  acid  on  saponifying  with  potash ;  it  is  purified 
by  precipitating  the  neutral  solution  with  basic  lead  acetate 
and  removing  the  lead  by  sulphuretted  hydrogen.2  It  is  also 
obtained  by  oxidizing  the  sulphamido-orthotoluic  acids  with 
potassium  permanganate  and  fusing  the  residue  with  potash,3 
and  is  formed  when  para-aldehydometahydroxybenzoic  acid,4 
a-chlorophthalic  acid,5  and  a-sulphophthalic  acid  6  are  fused  with 
caustic  potash  or  soda. 

It  is  tolerably  soluble  in  cold,  very  readily  in  hot  water  and 
alcohol,  and  crystallizes  in  large  stellate  groups  of  pointed  prisms 
which  melt  at  about  185°,  the  anhydride  being  formed  ;  on 
heating  with  dilute  hydrochloric  acid  to  180°,  it  decomposes 

1  Landshoff  and  Tiemann,  Bcr.  Deutsch.  Chem.  Ges.  xii.  1334. 
-  Baeyer,  ibid.  x.  1079.  3  Jacobsen,  ibid.  xiv.  42. 

4  Tiemann  and  Lamlshoff,  ibid.  xii.  1337. 

5  Kriiger,  ibid,  xviii.  1759. 

6  Griibe,  ibid,  xviii.  1130  ;  Ree,  Inaugurate.  Bern.  1886. 


HYDKOXYPHTHALIC  ACIDS.  493 

into  carbon  dioxide  and  metahydroxybenzoic  acid  (Ree).  Its 
aqueous  solution  is  coloured  reddish  yellow  by  feme  chloride. 
When  the  acid  is  heated  with  resorcinol,  hydroxyfluoresce'in  is 
obtained,  which  forms  a  dark,  yellowish  red  solution  in  caustic 
potash,  and  is  slightly  soluble  in  water  with  a  yellowish  green 
fluorescence;  acids  separate  it  from  its  alkaline  solution  as  a 
yellow  precipitate. 

a-Hydroxyphthalic  anhydride,  C8H404,  sublimes  in  feathery 
needles,  when  the  acid  is  heated  and  melts  at  165° — 166°. 

a-Methylhydroxyphthalic  acid,  C6H3(OCH3)(C02H)2,  is  formed 
by  the  oxidation  of  methylparahydroxyorthotoluic  acid  with 
potassium  permanganate,  and  crystallizes  from  water  in  stellate 
groups  of  needles,  which  lose  water  on  heating,  forming  the 
anhydride,  which  sublimes  in  long  needles  and  melts  at  930.1 

v-Hydroxyorthophthalic  acid  (3:1:2)  is  prepared  by  gently 
fusing  v-methylhy.droxyphthalic  acid  with  potash,  and  by  means 
of  the  diazo-reaction  from  the  product  of  reduction  of  a-nitro- 
phthalic  acid,  which  contains  amidophthalic  acid.  It  separates 
from  hot  water  as  a  compact,  crystalline  mass,  consisting  of 
short,  hard  prisms,  which  are  partly  converted  by  heating 
into  the  anhydride,  melting  at  145° — 148°,  and  are  partly  de- 
composed into  phenol  and  carbon  dioxide.  Its  aqueous  solution 
is  coloured  a  deep  cherry-red  by  ferric  chloride.  When  it  is 
heated  to  200°  with  resorcinol,  hydroxyfluorescem  is  formed. 

Dinitro-v-liydroxyphthalic  acid,  C6H(NO^)2(OH)(CO2H)2,  was 
first  obtained  by  the  action  of  nitric  acid  on  juglon,  a  hydroxy- 
naphthoquinone,  C10H5(OH)O2,  which  occurs  in  green  walnut 
shells  (Juglans  regia),  and  was  c&lled  juglonic  acid.  It  may  also 
be  prepared  by  the  nitration  of  v-hydroxyphthalic  acid ;  it  is 
exceptionally  soluble  in  water,  alcohol  and  ether,  and  separates 
from  petroleum  ether  in  small  crystals.  Its  acid  potassium  salt, 
C8H3KN2O9,  crystallizes  in  yellow,  rhombic  plates,  which  detonate 
violently  on  heating.  It  can  be  recrystallized  from  nitric  acid 
or  dilute  sulphuric  acid  without  undergoing  decomposition.2 

v-Mcthylhydroxyphthalic  acid  has  been  prepared  by  the 
oxidation  of  v-methylorthohomometahydroxybenzoic  acid ;  it  is 
tolerably  soluble  in  water,  and  crystallizes  in  microscopic  prisms, 
which  melt  at  160°,  and  are  thus  converted  into  the  anhydride, 
which  sublimes  in  needles  and  melts  at  87°.3 

1  Schall,  Ber.  Dcutsch.  Chem.  Ges.  xii.  829. 

2  Bernthsen  and  Semper,  ibid,  xviii.  210  ;  xix.  164. 

3  Jacobsen,  ibid.  xvi.  1962. 


494  AROMATIC  COMPOUNDS. 

2258  a-Hydroxyisophthalic  acid  (4:1:3)  is  formed,  together 
with  a  large  quantity  of  hydroxytrimesic  acid,  C6H2(OH)(C02H)3, 
when  carbon  dioxide  is  passed  over  disodium  salicylate  heated 
to  370° — 3800.1  It  may  be  obtained  in  a  similar  manner  from 
parahydroxybenzoic  acid,  which  first  changes  into  salicylic  acid.2 
It  is  also  formed  by  the  oxidation  of  para-aldehydosalicylic  acid 
or  ortho-aldehydoparahydroxybenzoic  acid  with  potassium  per- 
manganate, and  when  this  acid,3  a-metaxylenol,4  or  a-metaxylene- 
sulphonic  acid,5  is  fused  with  potash.  When  an  alkaline  solution 
of  salicylic  acid  is  heated  to  120° — 130°  with  tetrachloromethane, 
a-hydroxyisophthalic  acid  is  obtained,  together  with  a  little 
v-hydroxyisophthalic  acid.6 

In  order  to  prepare  it,  phenol  is  dissolved  in  an  alkaline  solu- 
tion which  contains  one  molecule  of  potash  to  three  of  soda,  the 
mass  evaporated  and  carbon  dioxide  passed  over  the  dry  residue 
for  some  time  at  120° — 160°,  the  temperature,  being  finally  raised 
to  300° — 320°.  The  chief  product  of  the  reaction  is  a-hydroxy- 
isophthalic acid  accompanied  by  parahydroxybenzoic  acid  and 
hydroxytrimesic  acid,  almost  two-thirds  of  the  phenol  coming 
over  unchanged.  The  residue  is  decomposed  with  hydrochloric 
acid,  and  the  a-hydroxyisophthalic  acid  repeatedly  recrystallized 
from  water.7 

It  forms  long  needles,  which  cross  each  other  at  an  angle  of 
60°,  melt  at  305°— 306°,  and  dissolve  at  10°  in  5,000,  at  24°  in 
3,000,  and  at  100°  in  160  parts  of  water.  It  is  readily  soluble 
in  alcohol  and  ether,  but  not  in  chloroform,  by  means  of  which 
it  can  be  separated  from  hydroxytrimesic  acid.  Its  aqueous 
solution  is  coloured  a  deep  cherry-red  by  ferric  chloride.  On  heat- 
ing to  200°  with  hydrochloric  acid,  it  decomposes  into  phenol 
and  carbon  dioxide,  while  on  dry  distillation  it  yields  salicylic 
acid,  phenol  and  carbon  dioxide.  When  its  disodium  salt,  C6H3 
(OH)(CO2Na)2,  is  heated  to  250°,  the  trisodium  salt,  C6H3(ONa) 
(CO2Na)2,  is  obtained,  together  with  phenol  and  carbon  dioxide, 
while  the  potassium  salt  yields  a  large  amount  of  parahydroxy- 
benzoic acid  when  heated  to  280°— 300°  (Ost). 

a-Methoxyisophthalic  acid,  C6H3(OCH3)(CO2H)2,  is  formed  by 

1  Ost,  Journ.  Pralcl.  Chem.  [2]  xiv.  99. 

2  Kupferberg,  ibid.  [2]  xvi.  423. 

3  Tiemann  and  Keimer,  Ber.  Deutsch.  Chem.  Ges.  x.  1571. 

4  Jacobsen,  ibid.  xi.  377. 

5  Jacobseu  and  Remsen,  ibid.  xi.  377. 

6  Hasse,  ibid.  x.  2195. 

7  Ost,  Journ.  Prakt.  Chem.  [2]  xv.  301. 


HYDROXYTEREPHTHALIC  ACID.  495 

the  oxidation  of  a-metaxylenyl  monomethyl  ether,1  or  methyl- 
parahomosalicylic  acid2  with  potassium  permanganate,  and 
crystallizes  from  hot  water  in  microscopic  needles,  melting 
at  261°  (Schall). 

Dimethyl  a-hydroxyisophthalate,  C6H3(OH)(CO2.CH3)2,  forms 
large,  flat  needles  which  melt  at  96°  (Jacobsen). 

Diethyl  a-Jiydroxyisophtlialate,  C6H3(OH)(CO2.C2H5)2,  crystal- 
lizes in  fine  needles,  which  melt  at  52°  and  are  soluble  in  caustic 
soda  (Ost). 

v-HydroxyisopTithalic  acid  (2:1:3)  is  formed  when  ortho- 
aldehydosalicylic  acid 3  or  sulphamido-isophthalic  acid  4  is  fused 
with  potash.  It  crystallizes  in  hair-like  needles,  which  melt  at 
243°— 244°,  dissolve  in  700  parts  of  water  at  24°,  and  in 
35-40  parts  at  100°.  Ferric  chloride  produces  a  cherry-red 
colouration ;  the  aqueous  and  alcoholic  solutions  show  a  bluish 
violet  fluorescence,  which  is  destroyed  by  alkalis.  The  acid  de- 
composes on  heating,  the  chief  portion  being  resolved  into 
salicylic  acid  and  carbon  dioxide. 

v-Methoxyisoplithalic  acid,  C6H3(OCH3)(C02H)2,  is  prepared  by 
the  oxidation  of  methylorthohomosalicylic  acid  and  crystallizes 
from  water  in  prisms,  which  melt  at  216° — 218°,  turning  brown 
and  subliming  at  the  same  time  (Schall). 

s-Hydroxyisophthalic  acid  (5  : 1 :  3)  is  obtained  by  fusing  s-sul- 
pho-isophthalic  acid  with  potash,  and  by  means  of  the  diazo- 
reaction  from  amido-isophthalic  acid.  It  crystallizes  from  hot 
water,  in  which  it  readily  dissolves,  in  fascicular  groups  of 
needles  with  two  molecules  of  water,  which  are  lost  at  100°. 
It  melts  at  288°  and  sublimes  in  broad,  lustrous  needles,  which 
dissolve  in  3280  parts  of  water  at  5°  and  are  coloured  a  faint 
yellow  by  ferric  chloride.  It  decomposes  into  phenol  and 
carbon  dioxide  on  distillation  with  lime  : 5 

Melting- 
point. 

Dimethyl  s-hydroxyisophthalate,  C6H3(OH)(CO2.CH3)2,  fine 

needles " 160° 

Diethyl  s-hydroxyisophthalate,  C6H3(OH)(CO2.C2H5)2  mono- 
clinic  prisms 103° 

2259  Hydroxyterephthalic  acid  (2:1:4)  was  prepared  by 
Warren  de  la  Rue  and  Muller  from  amidoterephthalic  acid  by 

1  Jacobsen,  Ber.  Deutsch.  Chem.  Ges.  xi.  898.  2  Schall,  ibid.  xii.  828. 

3  Tiemann  and  Riemer,  ibid.  x.  1570.  4  Jacobsen. 

6  Heine,  Ber.  Deutsch.   Chem.  Ges.  xii.  494  ;  Lonnies,  ibid.  xiii.  705. 


496  AROMATIC  COMPOUNDS. 

the  action  of  nitrous  acid.1  It  is  also  formed  when  paraxylenol,2 
bromoterephthalic  acid,8  ortho-aldehydometahydroxybenzoic  acid,4 
or  metahydroxyparatoluic  acid 5  is  fused  with  caustic  potash. 

In  order  to  prepare  it,  amidoterephthalic  acid  is  dissolved  in 
dilute  sulphuric  acid,  treated  with  sodium  nitrite  and  boiled.6 
It  forms  a  powder,  which  is  slightly  soluble  in  hot  water,  readily 
in  alcohol,  and  sublimes  on  heating  with  partial  decomposition 
without  previously  melting.  Its  aqueous  solution  is  coloured  an 
intense  violet-red  by  ferric  chloride.  When  it  is  mixed  with 
sand  and  submitted  to  dry  distillation,  it  decomposes  into  carbon 
dioxide  and  phenol,  and  on  heating  with  hydrochloric  acid  to 
220°  is  resolved  into  carbon  dioxide  and  metahydroxybenzoic 
acid,  while  fusion  with  an  excess  of  caustic  potash  converts  it 
into  salicylic  acid,  together  with  a  smaller  amount  of  metahy- 
droxybenzoic acid.7 

Methoxyterephthalic  acid,  C6H3(OCH3)(C02H)9,  is  formed  by 
the  oxidation  of  methylmetahomosalicylic  acid  8  and  crystallizes 
from  hot  water  in  small  prisms,  which  melt  at  277° — 279°,  and 
are  resolved  into  methyl  chloride  and  hydroxyterephthalic  acid 
by  hydrochloric  acid  at  160°. 

Dimethyl  hydroxyterephthalate,Q^±(Qi]£)  (CO2.CH3)2,  is  obtained 
by  passing  hydrochloric  acid  into  a  solution  of  the  acid  in  methyl 
alcohol,  and  crystallizes  in  splendid,  silky  needles,  which  melt  at 
94°  and  are  soluble  in  hot  water,  readily  in  alcohol.  Ferric 
chloride  gives  a  somewhat  fainter  colouration  than  with  the  free 
acid.  When  the  ethereal  solution  is  shaken  up  with  caustic 
soda  solution,  the  sodium  compound,  C6H3(ONa)(C02.CH3)2,  is 
formed  as  a  white  paste.  On  heating  the  acid  with  caustic 
soda,  methyl  iodide  and  wood-spirit,  the  trimethyl  ether,  C6H3 
(OCH3)(CO2.CH3)2,  is  obtained  as  an  oily,  pleasant-smelling 
liquid. 

Dimethyl  acetoxyterepUUate,  C6H3(OCO.CH3)(CO2.CH3)2,  is 
prepared  by  heating  the  dimethyl  ether  with  acetyl  chloride, 
and  crystallizes  from  alcohol  in  cauliflower-like  masses  of  fine 
needles,  melting  at  76°  (Burckhardt). 

Dinitrohydroxyterephthalic    acid,    C6H(NO,)(OH)(C02H)2,   is 

Ann.  Clicm.  Pharm.  cxxi.  96. 
Jacobsen,  Ber.  Deutsch.  Chem.  Ges.  xi.  570. 
Fischli,  ibid.  xii.  621. 
Tiemann  and  Landshoff,  ibid.  xii.  1336. 
Hall  and  Remsen,  ibid.  xii.  1433. 
Burckhardt,  x.  144. 
Earth  and  Schreder,  xii.  1260. 
8  Schall,  ibid.  xii.  828. 


HYDROXYMETHYLDIHYDROXYBENZOIC  ACIDS.         497 

formed  by  the  action  of  a  mixture  of  concentrated  nitric  acid  and 
fuming  sulphuric  acid  on  hydroxyterephthalic  acid.  It  is  readily 
soluble  in  water,  from  which  it  separates  in  golden  yellow,  trans- 
parent crystals,  resembling  those  of  calc-spar,  which  are,  like  the 
yellow  and  red  salts  of  the  acid,  explosive.1 


HYDROXYMETHYLDIHYDROXYBENZOIC 
ACIDS, 

XCH2.OH 
CflH8(OH)  / 

\CO.OH 

2260  In  1832,  Couerbe  detected  meconin?  C10H1004,  in  opium, 
and  Wohler  and  Liebig,  in  1842,  obtained  opianic  acid,3 
C10H10O5,  by  the  oxidation  of  narcotin  or  opian,  which  is  also  an 
opium  alkaloid.  This  acid  was  more  closely  investigated  by 
Wohler,  who  found  that  it  is  converted  by  further  oxidation  into 
hemipinic  acid,  C5H503.  He  assumed  that  in  its  formation  one 
molecule  of  opianic  acid  took  up  oxygen  and  formed  two  mole- 
cules of  hemipinic  acid  ;  he  says  :  "  It  contains  a  radical  which 
consists  of  half  the  radical  of  opianic  acid,  and  this  is  referred  to 
in  its  name."  * 

Anderson,  who  also  investigated  the  products  of  oxidation  of 
narcotin,  obtained  a  substance,  opianyl,  in  addition  to  these  acids, 
and  pointed  out  that  it  shows  an  interesting  relation  to  opianic 
and  hemipinic  acids  when  the  formula  of  the  latter  of  these  is 
doubled,  as  his  and  Laurent's5  researches  had  shown  to  be 
necessary.  "  For  we  have  as  follows  : 

Opianyl  .....  C10H10O4, 
Opianic  acid  .  .  .  C10H10O5, 
Hemipinic  acid  .  C10H1006, 

as  though  these  three  compounds  were  different  oxidation  pro- 
ducts of  the  same  radical." 6 

He  subsequently  found  that  opianyl  is  identical  with  me- 
conin.7 

Matthiessen  and  Foster  then  made  the  important  observation, 

1  Burckhardt,  Ber.  De.utsch.  Che.m.  Ges.  xii.  1273. 

2  Ann.  Chim.  Phys.  xlix.  44  ;  1.  337  ;  lix.  148. 

3  Ann.  Chem.  Pharm.  xliv.  126. 

4  Ibid.  1.1.  5  Compt.  Rend,  xx.  1118. 
6  Ibid.  Ixxxvi.  179.              7  Ibid,  xcviii.  44. 


49S  AROMATIC  COMPOUNDS. 

that  when  opiaiiic  acid  is  evaporated  with  caustic  potash  solution 
it  is  resolved  into  meconin  and  hemipinic  acid  : 


They  also  found  that  opianic  acid  is  reduced  to  meconin 
by  the  action  of  water  and  sodium  amalgam  : 

C10H1006+2H  =  C10H1004+H20. 

These  highly  characteristic  reactions  receive,  according  to 
them,  a  simple  explanation,  if  it  be  assumed  that  a  very  un- 
stable hydrate  of  meconin,  C10H12O6,  is  first  formed.  The  de- 
composition of  opianic  acid  then  becomes  quite  analogous  to 
that  of  benzaldehyde  into  benzyl  alcohol  and  benzoic  acid,  and 
the  reduction  of  the  former  also  corresponds  to  that  of  benzalde- 
hyde to  benzyl  alcohol. 

By  heating  hemipinic  acid  with  concentrated  hydriodic  acid, 
they  obtained  carbon  dioxide,  methyl  iodide  and  hypogallic  acid, 
according  to  the  equation  : 

C10H1006+2HI  =  C02  +  2CH3I  +  C7H6O4. 

If  hydrochloric  acid  be  employed,  metliylhypogallic  «c^,C8H8O4 
is  first  formed,  and  is  converted  into  hypogallic  acid  by  further 
heating. 

Hemipinic  acid,  therefore,  as  well  as  opianic  acid  and  meconin, 
contains  two  methyl  groups,  and  the  three  bodies  in  question 
are  derivatives  of  the  still  unknown  normal  compounds  : 

Normeconin  ....  CgH6O4, 
Noropianic  acid  .  .  C8H6O5, 
Norhemipinic  acid  .  C8H6O6, 

as  they  may  be  shortly  designated,  ordinary  meconin  being  thus 
dimethylnormeconin,  &c. 

They  then  succeeded  in  converting  the  latter,  as  well  as 
opianic  acid,  into  methylnor  meconin,  C9H8O4,  and  mdhylnor- 
opianic  acid,  C9H8O5,  by  heating  with  hydrochloric  or  hydriodic 
acid.  They  finally  considered  hemipinic  acid  to  be  dimethyl- 
dihydroxyterephthalic  acid  and  looked  upon  opianic  acid  as  the 
corresponding  aldehy  do-acid,1  but,  as  shown  by  Matthiessen  and 
Wright,  the  former  can  be  readily  converted  into  an  anhydride, 
and  must  therefore  be  dimethyldihydroxyphthalic  acid. 

1  Phil.  Trans.  1863,  345  ;  Journ.  Chem.  Soc.  [2]  i.  342  ;  ibid.  vi.  357- 


MECONIN  AND  OPIANIC  ACID.  499 

Liebermann  and  Chojnacld  proposed  the  following  formula 
for  opianic  acid  : 

/COH 
C6H2(OCH3)2< 

\CO.OH 

and  this  was  confirmed  by  the  researches  of  Beckett  and 
Wright,  who  also  found  that  hypogallic  acid  is  identical  with 
protocatechuic  acid. 

In  the  case  of  meconin  there  were  two  possibilities  ;  it  might 
be  either  hemipinic  aldehyde  or  the  anhydride  of  an  alcoholic 
acid: 

/COH  /CH2V 

C6H2(OCH3)2<  C6H2(OCH3)2<;         >O. 

CO  / 


The  facts  that  it  is  formed  from  opianic  acid  by  the  action  of 
nascent  hydrogen,  and  cannot  be  re-oxidized  to  opianic  acid, 
while  the  latter  is  converted  into  meconin  and  hemipinic  acid  by 
heating  with  caustic  potash,  are  in  favour  of  the  latter  view. 

Beckett  and  Wright  then  proved  that  this  view  is  correct,  and 
their  results  were  confirmed  by  the  researches  of  Hessert.1 
Hemipinic  acid  is  dimethylcatecholdicarboxylic  acid,  and  can 
readily  be  converted  into  protocatechuic  acid  or  catecholcarboxylic 
acid,  in  which  the  side-chains  have  the  position  C02H  :  OH  :  OH  = 
1  :  3  :  4.  Since  hemipinic  acid  is  simultaneously  a  derivative  of 
phthalic  acid,  the  second  carboxyl  group  must  be  either  in 
position  2  or  6  ;  in  the  latter  case  it  would  yield  only  one 
acid  methyl  ether,  while  in  the  '  former  two  such  compounds 
would  be  possible.  Wegscheider  has  now  found  that  two  such 
isomerides  exist,2  and  he  has  also  obtained  isovanillin  by  heating 
opianic  acid  with  dilute  hydrochloric  acid,3  while  Beckett  and 
Wright  found  that  methylvanillin  is  formed  when  sodium 
opianate  is  distilled  with  soda-lime. 

It  follows  from  these  facts  that  the  constitutions  of  the  three 
compounds  in  question  are  represented  by  the  following  formulae  : 

Meconin.  Opianic  acid.  Hemipinic  acid. 

CH2>0  COH  CO.OH 

o  /NcO.OH  /\CO.OH 

\/OCH3  \/OCH3 

OCH3  OCH3  OCH3 

1  Journ.  Chem.  Soc.  1876,  i.  164,  281,  461. 

2  Monatsh.  Chem.  iii.  348.  3  Ibid.  iii.  798. 


500  AROMATIC  COMPOUNDS. 

Meconin  therefore  stands  to  hemipinic  acid  in  the  same  rela- 
tion as  phthalide  to  phthalic  acid. 

2261 .  Meconinic  acid  or  Hydroxymetliyldimetlioxybenzoic  acid, 
C6H2(OCH3)2(CH2.OH)CO2H,  is  not  known  in  the  free  state. 
When  its  lactone,  meconin,  is  dissolved  in  baryta  water,  barium 
meconinate,  (C10HnO5)2Ba,  is  formed,  and  is  left  on  evaporation 
as  a  gummy  mass  *  (Kessert),  while  Prinz  obtained  it  in  fine, 
silky  needles.2  This  salt,  however,  yields  meconin  on  decom- 
position with  a  strong  acid.  The  copper  and  silver  salts  are  precipi- 
tates, which  decompose  on  heating  with  formation  of  meconin. 

Meconin,  C10H10O4,  as  already  mentioned,  occurs  in  opium. 
Anderson  obtained  it,  accompanied  by  other  products,  by  the 
oxidation  of  narcotin  with  nitric  acid,  and  it  is  also  formed  by  the 
reduction  of  opianic  acid. 

In  order  to  prepare  it,  the  mother  liquor  of  the  opium  alka- 
loids is  extracted  with  ether,  the  solution  evaporated,  and  the 
residue  washed  with  hydrochloric  acid  and  re-crystallized  from 
water  (Anderson).  It  forms  white,  lustrous  needles,  which  have 
a  bitter  taste,  melt  at  102°— 102°'5  (Wright),  and  when  carefully 
heated  sublime  in  splendid  needles.  It  is  readily  soluble  in 
alcohol  and  ether,  and  requires  22  parts  of  boiling  water  and 
700  parts  of  water  at  15'5°  for  solution.  On  heating  with 
concentrated  sulphuric  acid,  a  purple-coloured  solution  is  formed. 

It  forms  ethers  when  heated  with  stearic  or  be.nzoic  acids,  as 
was  shown  by  Berthelot,  who  concluded  from  this  that  it  is  an 
alcohol.3 

Chloromeconin,  C10H9C104,  was  prepared  by  Anderson  by  the 
action  of  chlorine  on  fused  meconin  or  on  its  aqueous  solution. 
It  crystallizes  in  colourless  needles,  which  are  scarcely  soluble  in 
cold,  somewhat  more  readily  in  hot  water,  and  more  freely  in 
alcohol,  melt  at  175°  and  sublime  without  decomposition. 

Bromomeconin,  C10H9Br04,  crystallizes  from  alcohol  in  colour- 
less needles,  melting  at  167°. 

lodomeconin,  C10H9IO4,  is  formed  by  the  action  of  chloride  of 
iodine  on  an  aqueous  solution  of  meconin,  and  forms  long 
crystals  or  needles,  which  melt  at  112°,  and  decompose  when 
more  strongly  heated. 

Nitromeconin,  C10H9(NO2)2O4,  is  obtained  by  dissolving  meconin 
in  cold,  concentrated  nitric  acid,  and  precipitating  with  water. 
It  crystallizes  from  alcohol  in  white  needles  or  prisms,  which 

1  Bcr.  Dcutsch.  Chem.  Ges.  xi.  240.          2  Journ.  Prakt.  Chem.  [2]  xxiv.  373. 
8  Ann.  Chim,  Phys.  [3]  Ivi.  51  ;  Ann.  Chem.  Pharm.  cxii.  356. 


MECONINIC  ACID.  501 


melt  at  160°,  and  sublime  when  carefully  heated.  It  forms  a 
yellow  solution  in  hot  alkalis  and  is  not  re-precipitated  by  acids, 
nitromeconinic  acid  being  probably  formed. 

Amidomeconin,  C10H9(NH2)O4,  is  prepared  by  warming  the 
preceding  compound  with  iron  filings  and  acetic  acid.  It  is 
precipitated  by  water  as  a  yellowish  powder,  which  is  only 
slightly  soluble  in  benzene,  and  melts  at  171°. 

Methyl  normeconin,  C6H2(OCH3)(OH)C2H2O2,  is  formed  when 
meconin  is  heated  with  hydrochloric  or  hydriodic  acid  (Mat- 
thiessen  and  Foster),  and  when  meconin  or  narcotin  is  carefully 
fused  with  caustic  potash  (Beckett  and  Wright).  It  crystallizes 
from  hot  water  in  prisms,  which  melt  at  125°;  ferric  chloride 
colours  the  aqueous  solution  a  beautiful  blue,  which  is  converted 
into  red  by  the  addition  of  ammonia.  On  further  fusion  with 
potash  it  is  converted  into  protocatechuic  acid. 

ty-Meconin.  When  hemipinimide,  which  will  be  further  de- 
scribed below,  is  boiled  with  tin  and  hydrochloric  acid,  hemi- 
pinimidine  is  formed  : 


CO  CH2 


(CH30)2C6H2(    >0      +  4H  =  (CH30)2<(    >O 
\C=NH  \0=NH 


+H0. 


This  substance  crystallizes  from  benzene  in  small  plates,  which 
melt  at  181°,  and  are  converted  into  nitrosohemipinimidine, 
C10H10O3N(NO),  by  the  action  of  sodium  nitrite  on  their 
solution  in  hydrochloric  acid.  The  latter  compound  crystallizes 
from  hot  alcohol  in  silky,  yellow  needles,  and  dissolves  in  caustic 
soda  solution  with  evolution  of  nitrogen.  Hydrochloric  acid 
added  to  this  solution  precipitates  ^-meconin,  which  crystallizes 
from  hot  water  in  colourless  needles,  melting  at  123°  —  124°. 
Its  isomerism  with  meconin  is  shown  by  the  following  formula  : 

co>0 

H. 


\/OCH; 


OCH, 

Nitro-ty-meconin,    C10H9(NO2)04,    crystallizes    in    splendid, 
yellowish  needles,  which  melt  at  166°. 

Amido-ty-meconin,  C10H9(NH2)O4,  resembles  amidomeconin, 
but  is  readily  soluble  in  benzene,  and  melts  at  1650.1 

1  Salomon,  Ber.  Deutsch.  Chem.  Gcs.  xx.  883. 
263 


502  AROMATIC  COMPOUNDS. 

Meconiosin,  C8H10O2,  also  occurs  in  opium,  and  crystallizes  in 
plates,  which  melt  at  88°  and  dissolve  in  27  parts  of  cold  water, 
and  in  almost  every  proportion  in  boiling  water.  On  heating 
with  sulphuric  acid  a  splendid  green  solution  is  formed.1 


ALDEHYDODIHYDROXYBENZOIC  ACIDS, 

XCOH 

CA(°H)<CO.OH 

2262  Noropianic  acid,  2C8H6O5  +  3H2O,  was  obtained  by 
Wright,  together  with  methyl  iodide,  by  boiling  opianic  acid 
with  four  times  its  weight  of  50  per  cent,  hydriodic  acid.  It  is 
readily  soluble  in  water  and  crystallizes  in  fine  prisms,  which 
become  anhydrous  at  100°  and  melt  at  171°.  Its  solution  is 
coloured  greenish  blue  by  ferric  chloride,  the  addition  of 
ammonia  or  carbonate  of  sodium  changing  the  colour  to 
brownish  red.  It  reduces  ammoniacal  silver  solution  in  the  cold 
and  forms  a  yellow  or  brown  solution  in  alkalis.  The  lead  salt 
is  a  canary-yellow  precipitate.2 

Methylnoropianic  acid,  C6H2(OCH3)OH(COH)C02H,  was 
prepared  by  Matthiessen  and  Foster  from  opianic  acid  by 
heating  it  with  hydrochloric  or  hydriodic  acid.  In  order  to 
prepare  it,  hydrochloric  acid  is  passed  into  a  warm  solution  of 
50  grms.  of  opianic  acid  in  600  cb.  cms.  of  strong  hydrochloric 
acid  until  no  opianic  acid  separates  after  standing  for  about  two 
days.  The  solution  is  then  concentrated,  the  paste  of  crystals 
thus  obtained  dissolved  in  water,  the  solution  neutralized 
exactly  with  ammonia  and*  treated  with  barium  chloride,  which 
produces  a  brown  precipitate.  The  addition  of  ammonia  to  the 
filtrate  precipitates  the  barium  salt  of  the  acid,  which  is  then 
washed  and  decomposed  with  sulphuric  acid.3 

It  is  readily  soluble  in  water  and  crystallizes  in  nacreous 
plates,  long  prisms,  or  transparent  vitreous  columns,  which  contain 
different  amounts  of  water,  but  all  readily  effloresce  in  the  air. 
The  anhydrous  acid  melts  at  154° ;  its  aqueous  solution  is 
coloured  dark  blue  by  ferric  chloride,  and  on  the  addition  of 
ammonia  light  red. 

1  T.  and  H.  Smith,  Pharm.  Journ.  Trans.  [3]  viii.  981. 

2  Journ.  Chem.  Soc.  1877,  ii.  545. 

3  Prinz,  Journ.  Prakt.  Chem.  [2]  xxiv.  368. 


OPIANIC  ACID.  503 


As  a  phenol-acid  it  forms  two  series  of  salts. 

Silver  methylnoropianate,  C9H705Ag,  is  a  gelatinous  precipitate, 
which  becomes  crystalline  on  standing.  It  is  soluble  in  hot 
water  and  separates  in  crystals  when  the  solution  is  cooled. 

Barium  methylnoropianate,  C9H6O5Ba  +  H2O,  is  also  thrown 
down  in  the  gelatinous  state  and  changes  into  granular  crystals 
on  standing. 

CUoromethylnoropianic  acid,  C6HC1(OCH3)OH(COH)C02H, 
is  obtained  by  the  action  of  potassium  chlorate  and  hydrochloric 
acid  on  methylnoropianic  acid,  and  crystallizes  from  hot  water  in 
large,  lustrous  needles,  which  melt  at  206°  (Prinz). 

Nitromethylnoropianic  acid,  C6H(N02)(OCH3)OH(COH)CO2H 
+  H2O,  is  formed  when  methylnoropianic  acid  is  treated  with 
dilute  nitric  acid  (Matthiessen  and  Foster).  It  is  also  obtained 
by  heating  nitro-opianic  acid  for  some  time  with  hydrochloric 
acid.  It  crystallizes  in  radiating  needles,  which  lose  their  water 
at  120°  and  melt  at  2030.1 

2263  Dimethylnoropianic  acid  or  Opianic  acid,  C6H2(OCH3)2 
(COH)CO2H,  was  prepared  by  Wb'hler  and  Liebig  from  narcotin 
by  boiling  it  with  dilute  sulphuric  acid  and  manganese  dioxide. 
Blyth  found  that  it  is  also  formed  by  heating  with  platinum 
chloride,2  and  Anderson  obtained  it  by  oxidizing  narcotin  with 
dilute  nitric  acid.  In  order  to  prepare  it  according  to  the 
method  proposed  by  Matthiessen  and  Foster,  100  grms.  of 
narcotin  are  heated  with  1,500  grms.  of  water  and  150  grms.  of 
sulphuric  acid  until  the  mixture  boils ;  150  grms.  of  finely 
powdered  pyrolusite,  corresponding  to  90  grms.  of  manganese 
dioxide,  are  then  added  somewhat  rapidly  and  the  hot  solution 
filtered. 

Opianic  acid  separates  out  on  cooling  and  is  purified  by 
recrystallization.  Wohler,  in  order  to  obtain  it  perfectly  colour- 
less, dissolved  it  in  sodium  hypochlorite,  heated  to  boiling,  and 
then  added  an  excess  of  the  hypochlorite.  The  decolourization 
may  also  be  effected,  according  to  Prinz,  by  passing  the  gases 
evolved  from  nitric  acid  and  arsenic  trioxide  through  the  hot 
solution ;  and  it  may  also  be  obtained  perfectly  white  by  running 
potassium  permanganate  into  the  hot  solution  acidified  with 
sulphuric  acid  until  it  becomes  sherry-yellow.3  The  portion 
which  is  left  in  the  mother-liquor  from  its  preparation  can  be 

1  Elbel,  Bcr.  Deutsch.  Chem.  Ges.  xix.  2306. 

2  Ann.  Chem.  Pharm.  1.  29. 

3  Prinz,  Journ.  Prakt.  Chem.  [2]  xxiv.  353. 


504  AROMATIC  COMPOUNDS. 

removed  by  ether,  which  does  not  dissolve  the  colouring  matter 
(Wegscheider). 

It  is  slightly  soluble  in  cold,  readily  in  hot  water,  alcohol  and 
ether,  and  crystallizes  in  thin,  narrow  prisms  or  silky  needles,  which 
melt  at  150°  (Wegscheider)  and  decompose  on  further  heating, 
giving  off  a  vapour  which  smells  like  vanilla  (Wohler).  It 
has  a  faint  acid  reaction  and  a  slightly  bitter  taste.  Sodium 
amalgam  and  water  reduce  it  to  meconin,  while  on  evaporation 
with  caustic  potash  it  is  converted  into  the  latter  and  hemipinic 
acid  (Matthiessen  and  Foster,  Beckett  and  Wright).  When  its 
sodium  salt  is  heated  with  soda  lime  methylvanillin  is  formed, 
and  isovanillin  when  it  is  heated  with  dilute  sulphuric  acid  to 
160° — 170°.  Concentrated  sulphuric  acid  converts  it  on  heating 
into  a  red  colouring  matter,  which  Anderson  mistook  for  alizarin, 
C14H8O4,  but  which  was  shown  by  Liebermann  and  Chojnacki  to 
be  the  closely  allied  substance  rufiopin,1  C14H8O6. 

The  salts  of  opianic  acid  have  been  investigated  by  Wohler 
and  Wegscheider.2 

Potassium  opianate.  C10H905K,  is  readily  soluble  in  water  and 
crystallizes  in  several  forms,  which  differ  in  the  amount  of  water 
they  contain.  It  crystallizes  from  ordinary  alcohol  in  compact, 
white  prisms  containing  two  and  a  half  molecules,  or  transparent, 
rhombic  tablets  with  one  molecule  of  water  of  crystallization. 

Barium  opianate,  (C10H9O5)2Ba  +  2H2O,  forms  a  radiating  mass 
of  prisms,  which  are  readily  soluble  in  water  and  effloresce  when 
kept  in  a  warm  place. 

Lead  opianate,  (C10H9O5)2Pb  -f  2H2O,  is  only  slightly  soluble, 
and  forms  very  lustrous,  transparent  crystals,  apparently  of  the 
same  form  as  sphenite. 

Silver  opianate,  2C10H9O5Ag  +  H20,  is  described  by  Wohler  as 
forming  short  prisms,  which  readily  become  coloured  yellow. 
Wegscheider  found  that  when  the  acid  is  rapidly  dissolved  in 
presence  of  silver  carbonate,  complete  saturation  does  not  take 
place,  and  that  reduction  ensues  on  boiling.  On  precipitating 
the  potassium  salt  with  silver  nitrate,  he  found  that  the  greater 
portion  of  the  silver  salt  was  removed  by  washing,  and  therefore 
prepared  it  by  mixing  concentrated  solutions  of  silver  fluoride 
and  potassium  opianate.  The  tough,  amorphous,  yellowish  pre- 
cipitate changes  on  stirring  into  hemispherical  or  warty  masses 
consisting  of  small  prisms,  which  can  be  completely  washed 
with  a  small  quantity  of  water. 

1  Ann.  Chem.  Pharm.  clxii.  321.  2  Monatsh.  Chem.  iii.  348. 


OPIANIC  ANHYDRIDE.  505 

Methyl  opianate,  C10H905(CH3),  was  prepared  by  Wegscheider 
from  the  silver  salt  by  the  action  of  methyl  iodide.  It  is  also 
formed,  as  found  by  Liebermann  and  Kleemann,  when  opianic 
acid  is  boiled  with  methyl  alcohol.1  It  crystallizes  from  alcohol 
in  flat,  monosymmetric  needles,  and  from  ether  in  thick,  vitreous 
tablets  or  short  prisms,  which  melt  at  102°  and  partially  sublime 
on  careful  heating.  It  rapidly  decomposes  into  methyl  alcohol 
and  opianic  acid  when  boiled  with  water,  the  latter  being  ob- 
tained pure  by  this  method  (Liebermann  and  Kleemann). 

Ethyl  opianate,  C10H9O5(C2H5),  is  readily  formed,  according  to 
Wohler,  by  saturating  a  hot,  alcoholic  solution  of  opianic  acid 
with  sulphur  dioxide,  while  it  could  not  be  prepared  by  means 
of  hydrochloric  acid.  Anderson,  however,  noticed  its  formation 
when  hydrochloric  acid  was  added  to  an  alcoholic  solution  of 
the  potassium  salt,  and  Prinz  prepared  it  by  the  action  of  the 
chloride  on  absolute  alcohol.  According  to  Liebermann  and 
Kleemann,  it  may  be  most  simply  obtained  by  boiling  the  acid 
with  absolute  alcohol. 

It  crystallizes  from  alcohol  in  needles  or  fine  prisms,  which 
melt  at  92°  and  sublime  when  carefully  heated. 

2264  Opianic  anhydride,  C20H18O9.  Wohler  found  that 
opianic  acid  undergoes  a  remarkable  change  when  it  is  kept  in 
a  state  of  fusion  for  some  time,  becoming  insoluble  in  water, 
and  he  assumed  that  it  is  thus  converted  into  an  isomeric  modi- 
fication, while  Matthiessen  and  Wright  concluded  that  it  loses 
water  and  forms  the  compound  C40H38019.2  Wegscheider,  on  the 
other  hand,  considered  the  substance  to  be  formed  from  three 
molecules  of  opianic  acid,  and  named  it  triopianide,  C30H18OU.3 ; 
Liebermann  has,  however,  found  4  that  it  is  formed  when  opianic 
acid  is  heated  for  two  hours  at  160°  in  a  current  of  air,  and 
explains  the  reaction  by  the  following  equation  : 

2(CH30)2(COH)C6H2,CO.OH  = 

(CH30)2(COH)C6H2.COV 

>O  +  H20. 
(CH30)2(COH)C6H2.C(K 

Opianic  anhydride  is  also  obtained  when  opianic  acid  is  heated 
with  phosphorus  pentachloride,  and  crystallizes  from  hot  acetone 
in  needles,  which  melt  at  234°. 

1  Bcr.  Dcutsch.  Chcm.  Gcs.  xx.  881.         2  Ann.  Chem.  Pharm.  Suppl.  vii.  63. 
3  Monatsh.  Chcm.  iv.  262.  4  Bcr.  Dcutsch.  Chcm.  Gcs.  xix.  2286. 


506  AROMATIC  COMPOUNDS. 

On  heating  with  caustic  potash  and  a  little  water,  it  decom- 
poses into  meconin  and  hemipinic  acid,  while  on  boiling  with 
caustic  potash  solution,  or  when  it  is  dissolved  in  sulphuric  acid 
and  the  solution  poured  into  water,  it  is  reconverted  into  opianic 
acid. 

Acetylopianic  acid.  When  aromatic  aldehydes  or  aldehydo- 
acids  are  heated  with  acetic  anhydride  and  anhydrous  sodium 
acetate,  the  aldehyde  group  CHO  is  converted  into  the  acrylic 
acid  residue  CH=CH  —  C02H.  Opianic  acid  does  not  behave 
in  this  way,  but  forms  acetylopianic  acid,  which  crystallizes  from 
hot  water  in  needles  melting  at  120°  —  121°.  It  is  insoluble  in 
cold  alkalis  and  is  only  decomposed  on  boiling,  acetic  and 
opianic  acids  being  formed  ;  it  therefore  does  not  contain  a 
carboxyl  group,  and  its  constitution  must  be  expressed  by  the 
following  formula  : 

/CO 
(CH30)2C6H2<   >0 

\CH.O.CO.CH3 

It  appears,  therefore,  that  opianic  acid  can  behave  not  only  as 
an  ortho-aldehydo-acid,  but  also  as  a  lactone.1  The  one  form 
can  pass  into  the  other  according  to  the  circumstances  of  the 
case: 

/CO.OH  /CO 

(CH30)2C6H  /  -  (CH30)2C6H2<    >0     . 

\CH.OH 


Opianyl  sulphurous  acid,  C6H2(OCH3)2(CHO.S03H2)CO2H,  is 
formed  when  opianic  acid  is  dissolved  in  a  hot  aqueous  solution 
of  sulphur  dioxide  : 


/CHO 
^CO.OH 


(CH30)2C6.H2/ -hSO(OH), 


(CH30)2C6H 

\CO.OH 

On  evaporation  at  a  gentle  heat,  the  compound  is  left  as  a 
fine  crystalline  mass,  which  is  resolved  into  its  constituents  by 
water.  Its  solution  has  a  characteristic  bitter  taste,  and  leaves 
a  persistent,  sweet  after-taste. 

1  Liebermann  and  Kleemann,  Ber.  Dcutsch.  Chem.  Ges.  xix.  2287. 


THIO-OPIANIC  ACID.  507 

Barium  opianyhulphitc,  (C10H10O5.SO3H)2Ba  +  3H20,  is  pre- 
pared by  dissolving  barium  carbonate  in  a  freshly  -made  solution 
of  the  acid,  and  crystallizes  in  lustrous,  rhombohedral  tablets. 

Lead  opianylsulphite,  (C10H10O5.SO2H)2Pb  +  6H20,  is  prepared 
in  a  similar  manner,  and  forms  very  lustrous,  four-sided  prisms 
or  six-sided  tablets  (Wohler). 

These  salts  correspond  to  the  ethidene  sulphites  (Part  II.  p.  73). 

2265  Thio-opianic  acid,  (CH3O)2C6H2(CHS)CO2H,  was  ob- 
tained by  Wohler  by  passing  sulphuretted  hydrogen  into  a  warm 
solution  of  opianic  acid  ;  it  forms  a  yellow  powder  which  crystal- 
lizes from  alcohol  in  fine,  transparent,  yellowish  prisms,  which 
melt  below  100°  and  resemble  opianic  acid  in  forming  an 
anhydride. 

Chloropianic  acid,  (CH30)2CHC1(COH)CO2H,  is  formed  by 
the  action  of  potassium  chlorate  on  a  hot  solution  of  opianic  acid 
in  hydrochloric  acid,  and  crystallizes  from  hot  water  in  small 
prisms  melting  at  210°—  211°  (Prinz). 

Bromopianic  acid,  (CH30)2C6HBr(COH)C02H,  is  prepared  by 
adding  bromine  to  a  boiling  solution  of  opianic  acid  (Prinz)  and 
by  triturating  opianic  anhydride  with  bromine  (Wegscheider). 
It  crystallizes  from  hot  water  in  small,  arborescent  needles  which 
melt  at  204°. 

Nitro-opianic  acid,  (CH3O)2C6H(NO2)(COH)C02H,  is  formed, 
together  with  nitrohemipinic  acid,  by  the  action  of  concentrated 
nitric  acid  on  opianic  acid.  It  is  only  slightly  soluble  in  water, 
and  crystallizes  in  lustrous  yellow  prisms,  melting  at  166°.  Its 
salts  are  readily  soluble  in  water  and  crystallize  well. 

Opianylplienylliydrazide,  C16H14N2O3,  is  obtained  by  mixing 
hot  solutions  of  opianic  acid,  phenylhydrazine  hydrochloride,  and 
sodium  acetate  (Part  III.  p.  283)  : 

5N2H3  =  C16H14N203 


It  crystallizes  from  alcohol  in  almost  colourless  needles,  which 
melt  at  175°,  and  are  insoluble  in  alkalis,  but  dissolve  in  con- 
centrated hydrochloric  acid,  from  which  solution  they  are  pre- 
cipitated by  water.  It  is  therefore  a  weak  base,  and  is  very 
stable,  being  unattacked  by  concentrated  sulphuric  acid  even  at 
130°  ;  it  has  probably  the  following  constitution  ; 

/CO—  N.C6H6 


508  AROMATIC  COMPOUNDS. 

Phenylhydrazine  nitro-opianic  acid,  C16HI5N306,  is  formed  in 
a  similar  manner,  according  to  the  equation  : 

/CO.OH 
(CH30)2C6H  (NO,)  <  +  NH2  -NH.C6H5 


/CO.OH 
(CH30)2C6H(N02K  +H20. 


=iN—  NHC6H5 

It  crystallizes  in  splendid,  carmine-red  needles,  which  melt  at 
184°,  and  form  a  red  solution  in  alkalis.  Acids  convert  it  into 
nitro-opianylphenylhydrazide,  C16H13N305,  which  crystallizes  in 
yellow,  silky  needles,  melting  at  173°,  is  insoluble  in  alkalis, 
and  behaves  as  a  weak  but  stable  base.1 

When  it  is  boiled  with  alcoholic  potash,  it  decomposes 
into  methyl  alcohol  and  nitromethylnoropianylwhenylhydrazide, 
C15HnN305,  which  has  also  been  prepared  from  methylnor- 
opianic  acid.2  This  substance  crystallizes  in  glittering,  yellow 
plates,  melting  at  191°,  and  since  it  is  a  phenol,  behaves  as  a 
weak  acid. 

Amido-opianylphenylhydrazide,  C16H15N303,  is  obtained  by  the 
reduction  of  the  nitro-compound  with  tin  and  hydrochloric  acid. 
It  crystallizes  in  fine  needles,  and  oxidizes  in  the  air  to  amido- 
hemipinylphenylhydrazide. 

2266  Isonoropianic  acid,  C6H2(OH)2(COH)C02H(C02H  : 
OH  :  OH  :  COH  1:3:4:5),  is  formed  when  the  following 
compound  is  heated  to  170°  —  180°  with  hydrochloric  acid.  It 
is  tolerably  soluble  in  cold,  readily  in  hot  water,  and  crystallizes 
in  yellowish  needles,  which  melt  with  decomposition  a  few 
degrees  above  240°.  Its  aqueous  solution  is  coloured  yellow 
by  alkalis  and  dark  green  by  ferric  chloride,  this  colour  being 
instantly  changed  to  reddish  violet  by  the  addition  of  ammonia. 
It  reduces  ammoniacal  silver  solution  in  the  cold,  and  Fehling's 
solution  on  boiling.3 

Methylisonoropianic  acid  or  Aldehydovanillic  acid,  C6H2(OCH3) 
(OH)COH(C02H),  is  formed,  together  with  vanillin,  when 
vanillic  acid  is  heated  with  caustic  soda  and  chloroform.  It 
is  readily  soluble  in  alcohol,  very  slightly  in  cold,  somewhat 
more  readily  in  boiling  water,  from  which  it  crystallizes  in  fine, 
silky  needles,  which  melt  at  221°  —  222°.  As  an  aldehydo-acid 

1  Liebermann,  Bcr.  Deutsch.  Chem.  Gcs.  xix.  763. 

2  Elbel,  ibid.  xix.  2306. 

3  Mendelsohn  and  Tiemann,  ibid.  x.  393. 


ISOPIANIC  ACID.  509 


it  combines  with  acid  sodium  sulphite ;  caustic  soda  colours  the 
solution  an  intense  yellow,  while  ferric  chloride  produces  a  dirty 
reddish  violet  colouration. 

Its  constitution  follows  from  the  fact  thai;,  in  the  synthesis  of 
aldehydes  or  aldehydo-acids  from  phenols  by  means  of  chloro- 
form, the  aldehyde  group  always  takes  either  the  ortho-  or  para- 
position  with  regard  to  the  hydroxyl.  Since  the  latter  is 
occupied  in  vanillic  acid,  the  aldehyde  group  must  lie  next  the 
hydroxyl,  and  the  two  groups  are  thus  found  in  aldehydovanillic 
acid  in  the  same  relation  as  in  salicyl aldehyde — a  view  which  is 
confirmed  by  its  behaviour  towards  caustic  soda  and  ferric 
chloride.1 

As  a  phenol  it  forms  two  series  of  salts.2 

Methyl  aldeJiydovanillate,  C6H2(OCH3)OH(COH)CO2.CH3,  is 
prepared  by  heating  the  acid  with  caustic  potash,  wood-spirit 
and  methyl  iodide,  and  forms  yellow  needles,  which  melt  at 
134° — 135°,  and  are  soluble  in  carbonates  of  the  alkalis. 

Isopianic  acid,  C6H2(OCH3)2(COH)CO2H.  The  methyl  ether 
of  this  compound  is  formed  together  with  the  foregoing  com- 
pound. It  crystallizes  from  boiling  water  in  fine  needles,  which 
melt  at  98° — 99°,  and  are  insoluble  in  the  alkali  carbonates. 
It  is  readily  saponified  by  hot  caustic  potash  solution.  The  free 
acid,  which  is  precipitated  by  acids  from  this  product,  crystallizes 
from  water  in  fine  needles,  melting  at  210° — 211°,  which  give  no 
colouration  with  caustic  soda  or  ferric  chloride.  It  forms  a 
slightly  soluble  compound  with  acid  sodium  sulphite.3 

Quercimeric  acid,  C8H6O5-hH2O.  This  substance,  which  is 
very  similar  to  isonoropianic  acid,  was  obtained  by  Hlasiwetz 
and  Pfaundler  by  fusing  quercitin  with  caustic  potash.  It 
forms  crystalline  granules  or  small  prisms,  is  readily  soluble  in 
water,  and  reduces  Fehling's  solution  and  salts  of  silver.  Ferric 
chloride  produces  a  blue  colouration  in  the  aqueous  solution, 
and  an  alkaline  solution  turns  red  in  the  air.  On  further  fusion 
with  potash  protocatechuic  acid  is  formed.4 

1  Ber.  Deutsch.  Ohem.  Ges.ix..  1278. 

2  Mendelsohn  and  Tiemann,  ibid.  x.  395.   , 

3  Ibid.   x.  397.  4  Mresber.  1864,  560. 


510  AROMATIC  COMPOUNDS. 


DIHYDROXYPHTHALIC  ACIDS,  C6H2(OH)2(C02H)2. 

2267  Hemipinic  acid  or  Dimethoxyortliophthalic  acid,  C6H2 
(OCH3)2(CO2H)2,  is,  as  already  mentioned,  a  product  of  the 
oxidation  of  opianic  acid,  and  has  also  been  obtained  by  the 
oxidation  of  the  alkaloids  contained  in  opium,  oxynarcotin  and 
narcein.1  It  is  readily  soluble  in  alcohol,  very  slightly  in  cold, 
more  freely  in  boiling  water,  from  which  it  crystallizes  in  colour- 
less, distorted  prisms  with  acute  basal  planes,  containing  two 
molecules  of  water  which  are  lost  below  100°.  The  anhydrous 
acid  melts  at  180°,  and  sublimes  in  lustrous  plates,  resembling 
those  of  benzoic  acid  (Wohler).  Crystals  containing  half  a 
molecule  of  water  are  obtained  by  the  spontaneous  evaporation 
of  its  solution,  while  those  deposited  from  a  supersaturated 
solution  contain  one  molecule  (Matthiessen  and  Foster).  It 
has  a  faint  acid  and  slightly  astringent  taste,  is  decomposed  into 
carbon  dioxide  and  dimethylcatechol  on  heating  with  soda-lime, 
and  is  converted  into  rufiopin  by  hot  sulphuric  acid.  Dilute 
hydrochloric  acid  decomposes  it  at  160° — 170°  into  methyl 
chloride,  carbon  dioxide,  isovanillic  acid  and  protocatechuic 
acid  (Wegscheider).  Its  aqueous  solution  is  coloured  yellowish 
brown  by  ferric  chloride,  and  gives  a  white  precipitate  with  lead 
acetate. 

Normal  potassium  hemipinate, Cw"H.8OoK2,  is  very  soluble  in 
water  and  does  not  easily  crystallize. 

Acid  potassium  hemipinate,  C10H906K,  forms  thick,  six-sided 
tablets,  which  are  readily  soluble  in  water  and  alcohol,  and  have 
an  acid  reaction. 

Normal  silver  hemipinate,  C10H8O6Ag2,  is  a  white  precipitate, 
insoluble  in  water. 

Acid  a-mcthyl  hemipinate,  C6H9(OCH3)2(CO2.CH3)C02H  + 
H20(OCH3:OCH3:C02CH3:C02H^4:  3:2:1),  is  prepared 
by  oxidizing  methyl  opianate  with  potassium  permanganate,  and 
crystallizes  from  hot  water  in  lustrous,  narrow,  flat  needles, 
which  readily  effloresce  and  when  completely  dehydrated  melt 
at  121° — 122°.  Its  solution  gives  a  yellowish  brown  precipitate 
with  ferric  chloride. 

1  Beckett  and  Wright,  Journ.  Chem.  Soc.  1876,  i.  461. 


HEMIPINIC  ACID.  511 


Acid  IB-methyl  hemipinate,  C6H2(OCH3)2(C02H)C02.CH3 
(4:3:2:1),  is  formed  by  passing  hydrochloric  acid  into  a  solu- 
tion of  hemipinic  acid  in  methyl  alcohol.  It  is  readily  soluble 
in  water  and  crystallizes  from  alcohol  in  arborescent  needles  or 
stellate  groups  of  prisms,  and  from  benzene  or  chloroform  in 
rhombic  tablets,  which  melt  at  137° — 138°.  Its  solution  is  not 
precipitated  by  ferric  chloride  (Wegscheider). 

Add  ethyl  hemipinate,  2C6H2(OCH3)2(CO2.C2H5)CO2H  + 
3H2O,  was  prepared  by  Anderson  by  passsing  hydrochloric  acid 
into  the  alcoholic  solution  of  the  acid.  It  is  also  formed 
by  heating  hemipinic  anhydride  with  90  per  cent,  alcohol 
(Matthiessen  and  Wright)  and  crystallizes  from  hot  water  in 
fascicular  groups  of  needles,  melting  at  141° — 142°  (Wegscheider). 
Its  solution  is  precipitated  by  ferric  chloride,  so  that  it  cor- 
responds to  the  a-methyl  ether,  and  not,  as  might  have  been 
expected  from  its  formation,  to  the  ^-compound. 

Hemipinic  anhydride,  C10H8O5,  is  formed  when  the  acid  is 
heated  for  an  hour  to  180°  (Beckett  and  Wright),  by  the  action 
of  phosphorus  pentachloride  on  the  acid  (Prinz)  and  by  the 
distillation  of  the  methyl  ether  (Wegscheider).  It  crystallizes 
from  absolute  alcohol,  benzene,  and  xylene  in  lustrous  needles, 
which  melt  at  167°  and  readily  sublime.  On  heating  with  zinc 
dust  and  glacial  acetic  acid  it  is  reduced  to  ^-meconin  (Salomon). 

2268  Nitrohemipinic  acid,  C6H(NO2)(OCH3)2(CO2H)2  +  H20, 
is  best  prepared  by  boiling  nitro-opianic  acid  with  pure  nitric 
acid.  It  is  also  formed  when  meconin  or  ijr-meconin  is  heated 
under  pressure  with  nitric  acid  (Salomon),  and  crystallizes  from 
hot  water  in  hard,  yellow,  vitreous  prisms  which  lose  water  on 
heating,  melt  at  155°,  and  are  converted  into  the  anhydride  at 
160° — 165°;  the  latter  crystallizes  from  benzene  incompact,  light 
yellow  prisms,  and  melts  at  1450.1 

Amidohemipinic  acid,  C6H(NH2)(OCH3)2(C02H)2,  was  first 
prepared  from  its  anhydride  and  was  then  obtained  by  Grime  by 
reducing  nitrohemipinic  acid  with  caustic  soda  and  ferrous 
sulphate.  The  free  acid  is  only  known  in  its  aqueous  solution, 
which  is  coloured  yellow,  showing  a  fine  green  fluorescence,  has 
an  acid  reaction  and  decomposes  on  evaporation. 

Barium  amidohemipinate,  C10H9N06Ba,  is  obtained  by  boiling 
the  anhydride  with  baryta  water ;  it  is  a  golden  coloured  crys- 
talline powder,  which  dissolves  in  dilute  acids,  but  is  insoluble 
in  water. 

1  Grime,  Ber.  Deutsch.  Chem.  Gcs.  xix.  2299. 


512  AROMATIC  COMPOUNDS. 

Anhydro-amidohemipinic  acid  was  prepared  by  Prinz  by  the 
action  of  an  acid  solution  of  stannous  chloride  on  a  boiling 
solution  of  nitro-opianic  acid  and  was  named  azo-opianic  acid.1 
Liebermann  then  pointed  out  that  this  substance  is  probably  the 
anhydride  or  anthranil  of  amidohemipinic  acid  : 2 

/CO.OH 
(CH30)2C6H/NH>0 

The  accuracy  of  this  view  was  proved  by  Grime.  It  crystallizes 
from  alcohol  in  fine,  colourless  needles,  which  melt  at  200°  with 
decomposition.  When  its  solution  in  concentrated  hydrochloric 
acid  is  evaporated,  the  hydrochloride  separates  in  stellate  groups 
of  prisms,  which  lose  their  hydrochloric  acid  on  drying.  Its 
potassium  salt,  (CH30)2CH(CONH)CO2K,  is  a  crystalline 
powder,  insoluble  in  alcohol.  When  it  is  boiled  with  acetic 
anhydride  and  anhydrous  sodium  acetate  the  acetyl-compound 
is  formed,  and  crystallizes  in  needles  which  form  an  aqueous  solu- 
tion possessing  a  blue  fluorescence.  It  readily  decomposes 
with  formation  of  free  acetic  acid,  and  has  the  following  con- 
stitution : 

/CO 
(CH30)2C6H(C02H)<  | 

XN.C2H30 

AmidohemipinylpTienylhydrazide  is  formed  by  the  continued 
boiling  of  anhydro-amidohemipinic  acid  with  alcohol,  phenyl- 
hydrazine  hydrochloride,  and  sodium  acetate,  and  also  by  the 
oxidation  of  amido-opianylphenylhydrazide  in  the  air  : 

XCO-NC6H5 
(CH30)2C6H^-CH=N         +  O  = 

jGO— NCJEL 


(CH30)2C6H— C  =  N         +  H20. 


XNH 

It  crystallizes  from  benzene  or  alcohol  in  small,  vitreous,  honey- 
yellow  crystals  belonging  to  the  tetragonal  system,  which  melt 
at  222.°8 

1  Journ.  Prakt.  Chem.  [2]  xxiv.  362. 

2  JSer.  Dcutsch.  Chcm.  Ges.  xix.  351. 
8  Liebermaixn,  ibid.  xix.  2275. 


HEMIPINIMIDE.  513 


Diazohemipinic    acid,    (CH3O)2C6H(CO2H)<^^>,  is  ob- 

tained by  the  addition  of  hydrochloric  acid  to  a  cooled  solu- 
tion of  sodium  amidohemipinate  and  sodium  nitrite.  It  forms  a 
light  yellow,  crystalline  powder,  which  explodes  by  percussion  or 
on  heating.  When  it  is  dissolved  in  warm  hydrochloric  acid,  the 
chloride,  (CH30)2C6H(CO2H)2N2C1,  separates  on  cooling  in  long 
needles,  which  are  instantly  converted  by  water  into  .their 
constituents  (Griine). 

Opianoxime  anhydride,  C10H9N04.  is  formed  when  an  alcoholic 
solution  of  opianic  acid  and  hydroxylamine  hydrochloride  is 
allowed  to  stand  : 

/CO.OH 

C6H2(OCH3)2<  +  H2N.OH  = 

XCOH 

/CO—  0 
C6H2(OCH3)2/      _|  +2H20. 

It  crystallizes  from  benzene  in  long  needles,  which  on  careful 
heating  melt  at  114°  —  115°,  and  are  converted  into  acid 
ammonium  hemipinate  by  boiling  with  water.1 

Hemipinimide,  C10H9NO4.  This  compound,  which  corresponds 
to  phthalimide,  is  formed  when  ammonium  hemipinate  is  heated 
and  when  an  alcoholic  solution  of  opianic  acid  is  boiled  with 
hydroxylamine  hydrochloride,  the  foregoing  compound  being 
first  formed  and  then  undergoing  an  intramolecular  change, 
which  also  occurs  when  it  is  rapidly  heated  to  117°;  the 
temperature  rises  suddenly  to  260°,  and  the  liquid  solidifies  on 
cooling  to  crystals  of  hemipinimide  : 

CO—  O  CO 

C6H2(OCH3)2 


It  crystallizes  from  hot  water  in  splendid  needles,  which  melt  at 
228°  —  230°  and  readily  sublime.  Its  aqueous  solution  has  a  fine 
blue  fluorescence.  When  it  is  triturated  with  a  cold  alcoholic 
solution  of  potash,  potassium  Jiemipinimide,  C10H8O4(NK),  is 
formed  as  a  crystalline  powder,  whose  aqueous  solution  gives  a 
white  precipitate  of  silver  hemipinimide,  C10H8O4(NAg),  with 
silver  nitrate. 

1  Licbermann,  Ber.  Deutsch.  Chem.  Ocs.  xix.  2923. 


514  AROMATIC  COMPOUNDS. 

Ethyl  hemipinimide,  C10H8O4(NC2H5),  is  obtained  when  the 
potassium  compound  is  heated  to  150°  with  ethyl  iodide.  It 
crystallizes  from  hot  water  or  benzene  in  needles,  which  melt  at 
96° — 98°.  The  solution  also  shows  a  blue  fluorescence.1 

2269  Methylnorhemipinic  acid,  C6H2(OCH3)OH(CO2H)2  + 
2H20  (4:3:2:1),  is  formed  by  heating  hemipinic  acid  with 
hydriodic  acid  for  a  short  time,2  and  by  heating  acid  a-methyl 
hemipinate  with  hydrochloric  acid.  It  forms  warty  crystals, 
which  are  readily  soluble  in  water  and  alcohol.  It  reduces 
ammoniacal  silver  solution  in  the  cold  and  Fehling's  solution  on 
heating,  gives  a  deep  blue  colouration  with  ferric  chloride,  and 
melts  at  152° — 155°  with  decomposition.  It  separates  from 
ether  as  an  anhydrous  powder,  which  melts  at  223° — 225°  with 
evolution  of  gas  (Wegscheider).  On  dry  distillation  it  decom- 
poses into  isovanillic  acid  and  carbon  dioxide,  and  is  converted 
into  protocatechuic  acid  by  fusion  with  potash. 

In  its  preparation  from  hemipinic  acid,  the  compound 
C9H6O4  +  2H20  is  formed  as  a  by-product.  It  crystallizes  in 
lustrous  prisms  or  thin  tablets,  which  melt  at  148°.  Its  aqueous 
solution  is  coloured  lilac  by  ferric  chloride. 

This  substance,  which  Liechti  named  opinic  acid,  might  be 
methylnorhemipinic  anhydride,  but  this  is  considered  doubtful 
by  Beckett  and  Wright  since  it  contains  water  of  crystallization, 
and  they  assume  that  it  corresponds  to  salicylide  and  has  the 
following  constitution : 

/C02H 

C6H(OCH3)^CO 
\O-> 

NitrometTiylnorhemipinic  acid,  C6H(NO2)(OCH3)OH(C02H)2, 
is  formed  when  methylnorhemipinic  acid  is  evaporated  with  dilute 
nitric  acid,  and  crystallizes  from  alcohol  in  almost  white,  silky 
needles,  which  are  readily  soluble  in  water,  and  melt  at  2200.3 

Amidomethylnorhemipinic  acid,  C6H(NH2)(OCH3)OH(CO2H)2, 
is  not  known  in  the  free  state;  its  barium  salt  separates  in 
lustrous,  dull  yellow  plates  when  the  anhydro-acid  is  boiled  with 
baryta  water. 

Anhydro-amidomethylnorhemipinic  acid, 

(CH30)(OH)C6H(C02H)<^>0,    is     prepared     by     adding 

1  Liebermann,  Ber.  Deutsch.  Chem.  Ges.  xix.  2287. 

2  Beckett  and  Wright,  loc.  cit.  ;  Liechti,  Ann.  Chem.  Plwirm.  Suppl.  vii.  149. 
8  Elbel,  Ber.  Deutsch.  Chem.  Ges.  xix.  2306. 


DIHYDROXYISOPHTHALIC  ACID.  515 

stannous  chloride  and  hydrochloric  acid  to  a  boiling,  saturated 
solution  of  nitromethylnoropianic  acid,  and  crystallizes  in  silky 
needles,  which  melt  at  174° — 175°  with  decomposition.  On 
boiling  with  acetic  anhydride  and  sodium  acetate,  the  diacetyl 
compound  is  formed : 

CH3(\  /CO 

)C6H(C02H)<  | 
CH3.CO.  CK  XN.  CO.CH3 

It  crystallizes  in  needles,  melting  at  205°,  and  yields  a  solution 
in  alcohol  which  has  a  blue  fluorescence.  Acetic  anhydride  is 
set  free  on  standing,  the  monoacetyl  derivative,  C6H(OCH3) 
(OC2H3O)(CO2H)(CONH),  being  formed.  This  body  melts  at 
198°  and  does  not  form  a  fluorescent  solution  in  alcohol. 

Isohemipinic  acid,  C6H2(OCH3)2(CO2H)2,  is  formed  by  the  oxi- 
dation of  methyl  isopionate  with  potassium  permanganate. 
The  methyl  ether  is  thus  obtained,  which  crystallizes  in  needles 
melting  at  167°,  and  yields  the  acid  on  saponification.  The 
latter  forms  white  needles,  which  are  scarcely  soluble  in  cold, 
more  readily  in  hot  water,  and  melt  at  245° — 246°  (Mendelsohn 
and  Tiemann). 

2270  Dihydroxyisophtlialic  acid,  or  Resorcinoldicar'boxylic  acid, 
C6H2(OH)2(CO2H)2.  When  resorcinol  is  heated  with  caustic 
soda  and  chloroform,  dihydroxyisophthalaldehyde,  C6H2(OH)2 
(COH)2,  is  formed,  which  is  almost  insoluble  in  cold  water,  but 
dissolves  readily  in  alcohol  and  ether,  from  which  it  is  removed 
by  agitation  with  acid  sodium  sulphite  without  forming  a 
difficultly  soluble  compound.  It  crystallizes  from  hot  water  in 
long,  strongly  refractive  needles,  which  melt  at  127°  and  readily 
sublime.  It  forms  a  yellow  solution  in  alkalis.  On  fusion  with 
caustic  potash  resorcinoldicarboxylic  acid  is  formed  ;  this  crys- 
tallizes from  water  in  fine,  white  needles,  which  decompose  on 
heating  into  resorcinol  and  carbon  dioxide.1  Its  constitution  has 
not  been  accurately  determined,  but  the  position  of  the  side- 
chains  is  probably  OH  :  OH  :  CO2H  :  CO2H  =  1:3:4:6,  since 
in  this  arrangement  the  carboxyls  stand  in  both  the  ortho- 
and  the  para-relation  to  the  hydroxyls. 

Dihydroxytercphthalic  acid,  (OH :  OH :  C02H :  C02H =1:4:2:5). 
This  body,  which  is  also  known  as  giiinoldicarboxylic  acid,  is  ob- 
tained by  passing  air  into  an  alkaline  solution  of  succinosuccinic 
ether  (Part  II.  p.  190 ;  III.  p.  146)  and  decomposing  the  pro- 

1  Lewy  and  Tiemann,  Ber.  Deutsch.  Chem.  Ges.  x.  2210. 


516  AROMATIC  COMPOUNDS. 

duct  with  sulphuric  acid.1  It  may  also  be  readily  prepared  by 
saponifying  the  ether,  and  crystallizes  from  hot  water  in  brownish 
yellow,  hair-like  needles,  but  from  alcohol  in  deep  yellow  plates, 
while  it  separates  from  ether  in  rhombic  tablets  or  prisms,  which 
are  coloured  greenish  yellow  and  show  a  light  blue  fluorescence. 
A  hot  supersaturated  solution,  however,  first  deposits  asymmetric 
white  and  green  crystals,  the  latter  of  which  are  less  acutely 
pointed  than  the  former.  On  further  cooling  the  rhombic  prisms 
appear  and  replace  the  asymmetric  crystals  when  the  solution  is 
again  gently  warmed.  If,  however,  the  latter  are  isolated,  the 
white  plates  are. converted  on  cooling  into  the  green,  which  again 
become  white  on  warming,  so  that  by  alternate  heating  and  cooling 
the  same  crystal  can  be  obtained  in  either  modification  an  in- 
definite number  of  times.  Since  the  shape  of  the  crystal  alters 
with  the  colour,  it  can  be  made  to  present  the  appearance  of  a 
concertina,  alternately  elongated  and  compressed  by  causing  the 
changes  of  temperature  to  follow  one  another  rapidly.2 

The  aqueous  solution  of  the  acid  shows  a  faint  emerald  green 
fluorescence,  while  that  of  the  alcoholic  solution  is  light  blue  ;  it  is 
coloured  a  pure  deep  blue  by  ferric  chloride.  When  rapidly  heated 
the  acid  decomposes  with  formation  of  quinol  and  other  products.3 

Normal  sodium  dihydroxyterephthalate,  C6H4O2(C02Na)2  + 
2H2O,  crystallizes  on  the  spontaneous  evaporation  of  its  aqueous 
solution,  in  flat,  light  brown  prisms. 

Acid  sodium  diliydroxyterephthalate,  C6H4O2(C02Na)C02H  + 
2H2O,  forms  light  yellow,  lustrous  prisms. 

Basic  sodium  dihydroxyterephthalate,  C6H2(ONa)2(CO2Na)2  + 
12H2O.  The  acid  dissolves  in  caustic  soda  forming  a  deep 
yellow  solution  with  a  strong  green  fluorescence ;  on  the  addition 
of  very  concentrated  caustic  soda  the  basic  salt  separates  in 
large  transparent  crystals,  which  possess  a  large  number  of  faces 
and  appear  a  faint  greenish  yellow  by  transmitted,  but  light  blue 
by  reflected  light. 

2271  Diethyl  diliydroxyterephthalate,  C6H4O2(C02.C2H5)2,  is 
formed  by  the  addition  of  bromine  to  a  solution  of  succinosuccinic 
ether  in  carbon  disulphide,4  and  by  the  action  of  sodium  on  an 
ethereal  solution  of  dibromaceto-acetic  ether,5  CH3.CO.CBr2.C02. 
C2H6.  The  latter  formation  corresponds  to  that  of  succino- 

1  Herrmann,  Ber.  Dcutsch.  Chem.  Ges.  x.  111. 

2  Lehmann,  Zeitsch.  Kryst.  x.  3  ;  Herrmann,  Ber.  Dcutsch.  Chem.  Ges.  xix.  2229. 

3  Herrmann,  Ann.  Chem.  Pharm.  ccxi.  335. 

4  Herrmann,  ibid.  ccxi.  372  ;  Ber.  Deutsch.   Chem.   Ges.  xvi.  1411 ;  Duisberg, 
ibid.  xvi.  133  ;  Ebert,  Ann.  Chem.  Pharm.  ccxxix.  45.     6  Wedel,  ibid,  ccxix.  71. 


DIHYDROXYTEREPHTHALIC  ACID.  517 

succinic  ether  from  monobromaceto-acelic  ether.  It  crystallizes 
from  ether  in  short,  thick  prisms  or  long  flat  needles,  and  from 
benzene  in  rectangular,  rhombic  tablets,  which  have  the  colour 
of  uranium  glass  and  show  a  light  blue  fluorescence.  It  melts 
at  133° — 133'5°  and  sublimes  at  a  higher  temperature  in  lustrous, 
green,  flat  plates  possessing  a  beautiful  blue  fluorescence.  Its 
alcoholic  solution  is  coloured  bluish  green  by  traces  of  ferric 
chloride.  It  dissolves  in  alkalis  forming  a  deep  yellow  solution, 
with  which  a  concentrated  solution  of  an  alkali  produces  a  deep 
orange-red  precipitate. 

Diethyl  diacetoxyterephtlialate,  C6H2(OCO.CH3)2(C02.C2H5)2,  is 
prepared  by  heating  the  ethyl  ether  with  acetyl  chloride,  and 
crystallizes  from  alcohol  in  colourless,  lustrous  plates,  which  melt 
at  115°  (Wedel). 

Monethyl  dihydroxyterephthalate,  C6H2(OH)2(CO2.C2H5)C02H. 
When  the  diethyl  ether  is  dissolved  in  dilute  caustic  potash 
and  the  unattacked  portion  removed  after  some  time  by  acetic 
acid,  barium  chloride  precipitates  the  barium  salt  of  the  acid 
ether  from  the  filtrate ;  this  salt  can  readily  be  recrystallized  from 
hot  water,  and  hydrochloric  acid  added  to  its  solution  precipitates 
the  mono-ethyl  ether  of  dihydroxyterephthalic  acid.  It  is  a 
strong  monobasic  acid,  crystallizes  from  hot  water  in  fine,  yellow 
needles,  and  is  deposited  on  the  evaporation  of  its  alcoholic  solu- 
tion in  light  yellow,  transparent,  vitreous  prisms,  which  melt  at 
184°.  Its  solution  is  coloured  bluish  violet  by  ferric  chloride. 

If  the  diethyl  ether  is  boiled  with  alcoholic  hydrochloric  acid 
and  zinc,  it  is  again  reduced  to  succinosuccinic  ether,  which  can 
therefore  be  regarded  as  the  ether  of  a  dihydroxydihydrotere- 
phthalic  acid.  The  latter  is  formed  in  the  first  stage  of  the 
reaction,  but  immediately  changes  into  the  isomeric  compound:1 

XC02.C2H5  Hx    XC02.C2H5 


C 


HC\/COH  H2C\  /CO 

C  C 

H/  \C02.C2H5  HX  \C02.C2H5 

The  latter  formula  is  rendered  probable  by  the  formation  of  the 
substance  from  bromaceto-acetic  ether,  CH3.CO.CHBr.CO2.C2H5, 
which  occurs  with  elimination  of  hydrobromic  acid  ;  it  also  forms  a 

1  Ber.  Deutsch.  Chem.  Ges.  xix.  428. 
264 


518  AROMATIC  COMPOUNDS. 

di-imide,  is  converted  into  an  oximido-compound  by  hydroxyl- 
amine  (Baeyer),  and  yields  both  a  phenylhydrazide  and  a  di- 
phenylhydrazide.1  On  the  other  hand  it  yields  a  diacetyl-com- 
pound  on  heating  with  acetyl  chloride  (  Wedel)  ,  which  is  more  readily 
obtained  by  adding  sodium  ethylate  to  its  ethereal  solution,  a 
rose-coloured  precipitate  of  C6H4O2Na2(CO2.C2H5)2  being  formed, 
which  is  immediately  converted  by  acetyl  chloride  into  the  com- 
pound C6H4(OC2H30)2(CO2.C2H5)2  (Baeyer).  The  latter  com- 
pounds must  be  looked  upon  as  derivatives  of  the  dihydroxy- 
dihydroterephthalic  acid  into  which  succinosuccinic  ether  or 
quinonetetrahydrodicarboxylic  acid  so  readily  changes. 

Dihydroxyterephthalic  acid  also  probably  exists  in  two 
forms,  as  quinoldicarloxylic  acid,  C6H2(OH)2(CO2H)2,  and  as 
quinonedihydrodicarboxylic  acid,  C602H4(CO2H)2,  which  readily 
change  into  one  another.  The  latter  formula  is  required  by 
its  formation  from  dibromaceto-acetic  ether,  while  its  whole 
behaviour  corresponds  to  the  former.  It  may  be  assumed  that 
the  green  modification  is  the  quinone-acid,  while  the  colourless 
is  the  quinol  derivative  (Herrmann). 

A  similar  case  has  been  observed  by  Baeyer  with  regard  to 
phloroglucinol,  which  forms  a  trioxime  with  hydroxylamine,  the 
trihydroxybenzene  being  converted  into  triketohexhydrobenzene 
(Part  III.  p.  186.):  2 

Phloroglucinol.  Triketohexhydrobenzene. 

OH  CO 

H2C/\CH2 


HO-C\/C-OH 
CH 

Analogous  cases  have  long  been  known  to  chemists  ;  among 
the  simplest  are  nitrous  acid  and  cyanic  acid,  which  are  exceed- 
ingly unstable  in  the  free  state,  but  yield  stable  modifications  of 

two  kinds  : 

Methyl  nitrite.  Potassium  cyanate. 

CH3—  0—  Ni=0  K—  O—  C=N 

Nitromethane.  Methyl  isocyanate. 

/°\ 

CH3—  N/    \  CH3—  N=C=:0 

1  Knorr,  Ber.  Deutsch.  CTiem.  Ges.  xvii.  2055. 
8  Ibid,  xviii.  3454  ;  xix.  159,  1800. 


TRI-  AND  TETRA-HYDROXYPHTHALIC  ACIDS.          519 

The  constitution  of  these  compounds  can  therefore  be  repre- 
sented with  equal  accuracy  by  different  structural,  or,  as  Laar l 
names  them,  tautomeric  formulae.  The  atoms  are  in  continual 
motion  within  the  molecule,  and  one  form  is  converted  into  the 
other  when  the  light  and  most  rapidly  moving  atoms  of  hydrogen 
are  more  strongly  attracted  by  one  or  other  of  the  remaining 
atoms.  If,  however,  the  hydrogen  be  replaced  by  a  heavier 
atom  or  molecule,  the  latter  no  longer  escapes  from  the  sphere 
of  attraction,  and  the  mobile  form  is  converted  into  a  stable 
one. 


TRIHYDROXYPHTHALIC   ACIDS,  C6H(OH)3(C02H)2. 

2272  Gallocarloxylic  acid,  C8H6O7  +  3H20,  is  formed,  together 
with  pyrogallolcarboxylic  acid  (p.  378),  when  pyrogallol  or  gallic 
acid  is  heated  to  130°  with  ammonium  carbonate.  It  requires 
3,000  parts  of  water  at  0°  for  solution,  and  crystallizes  from  hot 
water  in  very  fine  needles,  which  become  anhydrous  at  180° 
and  melt  above  270°  with  evolution  of  carbon  dioxide.  Dilute 
ferric  chlorides  colour  its  solution  violet,  while  the  concentrated 
reagent  produces  a  greenish  brown  colouration.  When  heated 
in  the  air  with  water  and  an  excess  of  calcium  carbonate,  the 
latter  is  coloured  reddish  violet,  and  when  an  ammoniacal  solu- 
tion of  the  acid  is  mixed  with  a  solution  of  bicarbonate  of 
calcium,  a  deep  violet  coloured  precipitate  is  formed,  which  may 
therefore  be  obtained  with  spring  water  containing  calcium 
carbonate.2 


TETRAHYDROXYPHTHALIC  ACIDS, 
C6(OH)4(C02H)2, 

2273  TetraJiydroxyterephthalic  acid.  When  an  ethereal  or 
alcoholic  solution  of  ethyl  dihydroxyterephthalate  is  treated  with 
anhydrous  nitrogen  trioxide,  it  is  converted  into  ethyl .  dihydr- 
oxyguinoneterephthalate,  C6O2(OH)2(CO2.C.2H5)2,  crystallizing  in 
yellow  prisms,  which  are  slightly  soluble  in  cold  water,  alcohol 
and  ether,  more  readily  in  chloroform.  The  solutions  have  a 

1  Ber.  Deutsch.  Chem.  Ges.  xviii.  648  ;  xix.  730. 

2  Brunner  and  Senhofer,  Monatsh.  CJicm.  i.  468. 


520  AROMATIC  COMPOUNDS. 

deep  yellowish  red  colour.  When  the  ether  is  heated  with  caustic 
soda,  a  basic  salt  of  dihydroxyquinonetere.phthalic  acid  is  formed, 
and  immediately  decomposes  on  the  addition  of  acids  into  carbon 
dioxide  and  dihydroxyquinone,  C6O2H2(OH)2,  which  forms  small, 
black-brown  crystals.  Nitranilic  acid,  Cb02(N02)2(OH)2,  is 
always  formed  if  dihydroxyterephthalic  acid  be  submitted  to  the 
same  treatment. 

Ethyl  tetrahydroxyterephthalate,  C(.(OH)4(C02.C2H5)2,  is  ob- 
tained by  passing  sulphur  dioxide  into  a  faintly  alkaline  solution 
of  the  dihydroxyquinone  ether,  and  crystallizes  from  hot  chloro- 
form in  golden  yellow  plates,  melting  at  178°.  It  is  converted 
by  cold  caustic  soda  solution  into  sodium  tetrahydroxytere- 
phthalate,  C6(OH)4(CO2Na)2,  which  crystallizes  in  yellow  prisms. 
On  decomposition  with  sulphuric  or  hydrochloric  acid,  tetra- 
hydroxyphthalic  acid  yields  carbon  dioxide  and  tetrahydroxy- 
benzene,  C6H2(OH)4,  which  forms  yellow  needles,  melting  at 
1480.1 

1  Loewy,  Ber.  Deutsch.  Chem.  Ges.  xix.  2385. 


INDEX 


INDEX. 


A. 


ACETBROMAMIDE,  113 

Acetmetamidobenzoic  acid,  248 
Acetmetatoluide,  62 
a-Acetmetaxylide,  407 
*-Acetmetaxylide,  407 
•u-Acetmetaxylide,  406 
Acetmethylparatoluide,  65 
Acetometahydroxybenzidene   acetate, 

293 

Acetortho-amidobenzoic  acid,  239 
Acetorthotoluide,  59 
a-Acetorthoxylide,  406 
•y-Acetorthoxylide,  406 
Acetoxiine  benzyl  ether,  98 
Acetparamidobenzoic  acid,  253 
Acetparatoluide,  66 
Acet.paraxylide,  407 
Acetphthalimide,  464 
Acetylbenzenylamidoxime  214 
Acetylisovanillic  acid,  354 
Acetylmetahydroxybenzaldehyde,  293 
Acetylopianic  acid,  506 
Acetylorthamidobenzaldehyde,  149 
Acetylparahydroxybenzaldehyde,  295 
Acetylparahydroxybenzidene     acetate, 

296 

Acetylparamidobenzaldehyde,  150 
Acetylsalicylie  acid,  308 
Acetyl  salicylaldehyde,  288 
Acetylsinapic  acid,  377 
Acetylvanillic  acid,  353 
Acetylvanillin,  347 
Acid  ammonium  hippurate,  189 
Acid  ammonium  phthalate,  456 
Acid  barium  hydroxamate,  208 
Acid  barium  orthosulphobenzoate,  268 
Acid  bariumphthalate,  457 
Acid  calcium  benzarsenate,  277 
Acid  ethyl  hemipinate,  511 
Acid  ethyl  metasulphobenzoate,  271 
Acid  ethyl  o-nitrophthalate,  474 
Acid  ethyl  v-nitrophthalate,  474 
Acid  metatoluidine  oxalate,  61 
Acid  a-methyl  hemipinate,  510 
Acid  /3-methyl  hemipinate,  511 


Acid  methyl  sulphinidephthalate,  478 
Acid  paratoluidine  oxalate,  64 
Acid  potassium  benzarsenate,  277 
Acid  potassium  benzhydroxamate,  208 
Acid  potassium  benzophosphinate,  276 
Acid  potassium  hemipinate,  510 
Acid    potassium    sulphinidephthalate, 

477 
Acid    potassium     sulphoparahydroxy- 

benzoate,  336 
Acide  quinique,  382 
Acid  silver  sulphinidephthalate,  478 
Acid  sinapin  sulphate,  375 
Acid  sodium  benzhydroxamate,  208 
Acid  sodium   dihydroxyterephthalate, 

516 
Addition  products  of  isophthalic  acid, 

481 
Addition  products   of   phthalic    acid, 

469 
Addition  products  of  terephthalic  acid, 

486 

Adjacent  Dinitroparatoluidine,  71 
Adjacent  metadihydroxybenzoic   acid, 

360 

Aes-cioxalic  acid,  363 
Aldehydes,  447 
Aldehydovanillic  acid,  508 
Aldehydohydroxybenzoic     acids,    491, 

502 

Alizaric  acid,  450 
Allyl  benzoate,  162 
Aloi'sol,  402 
Amarine,  140 
Amarythrin,  428 
Amido-anisic  acid,  338 
Amido-azotoluenes,  77 
Amid  obenzenyl-phenylene-amidine,  206 
Amidobenzoic  acid  percyanide,  248 
Amidobenzylamines,  120 
Amido-derivatives  of  the  xylenes,  405 
Amidohemipinic  acid,  511 
Amidohemipinylphenylphydrazide,  512 
Amido-isophthalic  acid,  482 
Amidomeconin,  501 
Amidometa-azotoluene,  78 
Amidometatoluic  acids,  418 


524 


INDEX. 


Amidomethylnorhemipinic  acid,  514 
Amido-opianylphenylhydrazide,  508 
Amidortho-azotoluene,  77 
0-Amido-orthocresol,  26,  51 
7-Amido-orthophenol,  26 
Amido-orthotoluic  acids,  415 
Ainido-\|/-meconin,  501 
a-Amidoparacresol,  20 
j8-Amidoparacresol,  30 
7-Amidoparacresol,  30 
Amidoparahydroxybenzoic  acid,  335 
a-amidoparatoluic  acid,  421 
Amidophenylmetabenzoglycocyamine, 

253 

Amidophthalic  acids,  475 
a-Amidophthalic  acid,  475 
v- Amidophthalic  acid,  475 
o-Amidosalicylic  acid,  317 
/8-Amidosalicylic  acid,  318 
Amido-substituted  benzylamines,  116 
Amidosulphobenzoic  acids,  275 
Amidoterephthalic  acid,  489 
Amidotoluenes,  54 
Amido-uramidobenzoyl,  242 
Amidoxylenes,  405 
Ammonium  benzidene  sulphate,  137 
Ammonium  benzoate,  160 
Ammonium  gallate,  368 
Ammonium  metahydroxybenzoate,  321 
Ammonium  parahydroxybenzoate,  328 
Ammonium  salicylate,  303 
Ammonium  tcrephthalate,  484 
Amyg-dalacese,  131 
Amygdalin,  130 
Amyl  benzoate,  162 
Amyl  hippurate,  191 
Amyl  orsellinate,  433 
Amyl  salicylate,  306 
Anhydrides  of  parahydroxybenzoic  acid, 

331 

Anhydro-amidohemipinic  acid,  512 
Anhydro  -  amidomethylnorhemipinic 

acid,  514 

Anhydrobenzodiamidobenzene,  205 
Anhydrous  benzoic  acetic  acid,  167 
Aniletic  acid,  316 
Anilido-ethoxytolu-quinone       anilide, 

49 

Anilidohydroxytoluquinone,  49 
Anilidohydroxytoluquiuone  anilide,  49 
Aniline,  297 

Aniline  lourde  speciale,  56 
Aniline  oil,  55 
Aniline  orange,  31 
Anis-amide,  333 
Anis-anilide,  333 
Anisbenzanishydroxylamine,  312 
Anisbenzethylhydroxylamine,  340 
Anisbenzhydroxamic  acid,  340 
Anis-dibenzhydroxylamine,  341 
Anise  alcohol,  284 
Anisenyloxime  compounds,  339 
Anisethylbenzhydroxylamine,  341 
Anishydroxamic  acid,  339 


Anisic  acid,  329 

Anisic  acid,  substitution  products  of, 

336 

Anisic  anhydride,  332 
Anisonitril,  334 
Anisuric  acid,  333 
Anisyl  chloride,  332 
Anthranil,  240 

Anthranilcarboxylic  acid,  240 
Anthranilic  acid,  297 
Antimony  derivatives  of  toluene,  86 
Archil,  42 

Arsendiparatolyl  chloride,  85 
Arsendiparatolyl  trichloride,  85 
Arsenditolyl  oxide,  85 
Arsenic  Compounds  of  Benzyl,  125 
Arsenic  derivatives  of  toluene,  84 
Arsenobenzoic  acid,  277 
Arsenorthotolyl  chloride,  85 
Arsenorthotolyl  dioxide,  86 
Arsenorthotolyl  oxide,  85 
Arsenparatolyl  chloride,  84 
Arsentolyl  oxide,  85 
Arsentribenzoic  acid,  278 
Arsentritolyl  dichloride,  85 
Asymmetric  diamido-azotoluene,  80 
Asymmetric    dibenzyl    thiocarbamide, 

124 

Asymmetric  dibenzyl  urea,  123 
Asymmetric  ethylbenzoyl  urea,  178 
Asymmetric        metadihydroxy  benzoic 

acid,  359 
Asymmetric  diphenylbenzenylamidine, 

204 

Azo-aceto-acetic  benzoic  acid,  267 
Azobenzenesalicylic  acid,  319 
Azobenzoic  acids,  265 
Azo-derivatives  of  benzoic  acid  265 
Azo-derivatives  of  toluene,  75 
Azomalonic-benzoic  acid,  268 
Azonitromethanebenzoic  acid,  267 
Azo-orcin,  52 
Azophenylmethyl,  181 
Azo-opianic  acid,  512 
Azotoluenes,  75 
a-Azotoluidine,  79 
0-Azotoluidine,  79 
Azoxybenzoic  acids,  265 
o-Azoxytoluidine,78 
/3-Azoxytoluidine,  79 


B, 


BADIANIC  ACID,  329 
Barbatic  acid,  402,  435 
Barium  amidohemipinate,  511 
Barium  benzoate,  161 
Barium  benzylsulphonate,  108 
Barium  chlorobenzylsulphonate,  108 
Barium  diamidobenzoate,  259 
Barium  o-dinitrobenzoate,  234 
Barium  )8-dinitrobenzoate,  234 
Barium  7-dinitrobenzoate,  234 


INDEX. 


525 


Barium  8-dinitrobenzoate,  235 

Barium  e-dinitrobenzoate,  235 

Barium  dinitrosalicylate,  317 

Barium  gallate,  369 

Barium  hippurate,  189 

Barium  homohydroxysalicylate,  438 

Barium  isophthalate,  479 

Barium  lecariorate-,  434 

Barium  meconinate,  500 

Barium  metabromobenzoate,  224 

Barium  metahydroxybenzoate,  321 

Barium  metanitrobenzoate,  231 

Barium  methylnoropianate,  503 

Barium  opianate,  504 

Barium  opianylsulphite,  507 

Barium  ornithurate,  193 

Barium  orsellinate,  432 

Barium  orthobromobenzoate,  223 

Barium  orthonitrobenzoate,  230 

Barium  parabromobenzoate,  224 

Barium  parahydroxybenzoate,  328 

Barium  paranitrobenzoate,  232 

Barium  para-orsellinate,  436 

Barium  protocatechuate,  352 

Barium  pyrogallolcarboxylate,  379 

Barium  quinate,  384 

Barium  salicylaldehyde,  287 

Barium  salicylate,  303 

Barium  terephthalate,  484 

Basic   barium  nitroparahydroxybenzo- 

ate,  335 

Basic  copper  potassium  salicylate,  304 
Basic  copper  quinate,  384 
Basic  lead  pyro-gallolcarboxylate,  379 
Basic  sodium  dihydroxyterephthalate, 

516 

Benzaldehyde,  129 
Benzaldehyde-green,  135 
Benzaldehyde  oxyiodide,  137 
Benzaldoxime,  139 
Benzamic  acid,  246 
Benzamide,  172,  199 
Benzamide  hydrochloride,  174 
Benzanilide,  174 
Benzanilidimidocbloride,  203 
Benzanisbenzhydroxylamine,  341 
Benzanishydroxamic  acid,  340 
Benzarsene  chloride,  277 
Benzarsene  iodide,  277 
Benzarsenic  acids,  277 
Benzarsenious  acid,  277 
Benzdianishydroxylamine,  342 
Benzene,  297 
Benzenyl  alcohol,  194 
Benzenyl  amidines,  1 95 
Benzenylamidophenate,  206 
Benzenylamidothiophenate,  206 
Benzenylamidoxime,  212 
Benzenylamidoximemetacarboxylic 

acid,  480 
Benzenylamidoximeparacarboxylic 

acid,  485 
Benzenylazoximebenzenylcarboxylic 

acid,  468 


Benzenylazoxime  carbinol,  215 

Benzenylazoxime  propenylcarboxylic 
acid,  215 

Benzenyl  compounds,  194 

Benzenylethoxime  chloride,  213 

Benzenylethenylazoxime,  214 

Benzenyl  ethyl  ether,  196 

Benzenyloxime  compounds,  207 

Benzenyloximic  acid,  208 

Benzenyl  triacetate,  196 

Benzenyl  tribromide,  196 

Benzenyl  trichloride,  195 

Benzenyltrichlorophosphoryl  chloride, 
311 

Benzethylanishydroxylamine,  341 

Benzethylbenzhydroxylamine,  209 

Benzhydroxamic  acid,  208 

Benzhydroxamide,  212 

Benzhydroxylamine,  207 

Benzidene-acetamide,  143 

Benzidene-aniline,  140 

Benzidene-aniline  cyanhydrate,  141 

Benzidene  benzoate,  163 

Benzidene  benzobromohydrin,  170 

Benzidene  benzochlorohydrin,  169 

Benzidene  compounds,  136 

Benzidene  diacetate,  137 

Benzidene  di bromide,  136 

Benzidene  dichloride,  136 

Benzidene  dichlorochromic  acid,  6 

Benzidene  diethyl  ether,  136 

Benzidene  di-iodide,  137 

Benzidenedimethylparadiamido- 
benzene,  142 

Benzidenediphenylhydrazine,  141 

Benzidenedi-ureide,  143 

Benzidene-orthodiamidobenzene,  141 

Benzideneparadiamidobenzene,  1 42 

Benzidenephenylamine  hydrochloride, 
143 

Benzidenephenylhydrazine,  141 

Benzidenephenyldiamine,  142 

Benzidene  sulphide,  138 

Benzidenetetra-ureide,  143 

Benzidenetri-ureide,  143 

Benzidene  ureides,  143 

Benzidene  urethane,  143 

Benzidenoxime,  139 

Benzimido-acelic  ether,  201 

Benzimido-amide,  202 

Benzimido-ethers,  200 

Benzimido-ethyl  ether,  201 

Benzimido-isobutyl  ether,  201 

Benzimido-thiobenzyl  ether,  202 

Benzimido-thio-ethyl  ether,  201 

Benzoene,  3 

Benzoene  monochlore,  7 

Benzoic  acid,  7,  108,  151,  297,  383 

Benzole  acid,  azo-derivatives  of,  265 

Benzoic   acid,    nitro-substitution    pro- 
ducts of,  227 

Benzoic  acid,  salts  and  ethers  of,  160 

Benzoic  anhydride,  166 

Benzoleic  acid,  159 


526 


INDEX. 


Benzonitril,  122,  197 

Beuzonitril  and  its  derivatives,  197 

Benzophosphine  chloride,  276 

Benzophosphinic  acid,  275 

Benzolorthoalcoholsame,  442 

Benzortho-amidobenzoic  acid,  239 

o-benzothio-aldehyde,  138 

0-benzothio-aldehyde,  138 

7-benzothio-aldehyde,  139 

Benzo-trichloride,  195 

Benzoxamidine,  213 

Benzoyl,  285 

Benzoyl  acetyl  oxide,  167 

Benzoylaniline,  174 

Benzoylanthranil,  241 

Benzoylazo  benzene,  180 

Benzoylbenzenylamidoxime,  214 

Benzoyl-benzoic  acid,  458 

Benzoylbenzoximic  acid,  209 

Benzoyl  bromide,  169 

Benzoyl  chloride,  168 

Benzoyl    derivatives    of    amines    and 

amido- bases,  174 
Benzoyl  dioxide,  167 
Benzoyldiphenylamine,  175 
Benzoyldiphenylhydrazine,  181 
Benzoyl  disulphide,  171 
Benzoyl  ethylbenzhydroxamate,  209 
Benzoyl  fluoride,  170 
Benzoyl-glycollic  acid,  165 
Benzoyl  group,  128 
Benzoylguanidine,  243 
Benzoylguanidine,  nitrate,  243 
Benzoyl,  halogen  compounds  of,  168 
Benzoylhelicin,  289 
Benzyl  hydrosulphide,  138 
Benzoyl  iodide,  170 
Benzoyl-lactic  acid,  165 
Benzoylmethylaniline,  175 
Benzoylmethylpyrogallol         dimethyl 

ether,  164 

Benzoylnitranilines,  175 
Benzoyl,  nitrogen  compounds  of,  172 
Benzoylornithine,  193 
Benzoylorthotoluide,  175 
Benzoyl  oxide,  166 
Benzoyl,  oxides  of,  166 
Benzoyl  paratoluide,  175 
Benzoyl  peroxide,  167 
Benzoylphenylhydrazine,  179 
Benzoylpropylpyro  -  gallol      dimethyl 

ether,  164 

Benzoyl pyro-gallol  dimethyl  ether,  164 
Benzoylsalicin,  282 
Benzoyl  salicylaldehyde,  288 
Benzoylsalicylarnide,  312 
Benzoylsalicylnitril,  313 
Benzoyl  sulphide,  171 
Benzoylsulphimide,  269 
Benzoyl,  sulphur  compounds  of,  170 
Benzoyl  thiocyanate,  172 
Benzoyl  thio-urea,  179 
Benzoyl  urea,  178 
Benzoyl vanillic  acid,  353 


Benzyl,  89 

Benzylacetamide,  121 

Benzyl  acetate,  97 

Benzyl  alcohol,  7,  89  ;  properties,  93  ; 

substitution  products  of,  98 
Benzylamidine,  202 
Benzylamine,  112  ;  properties,  113 
Benzylamine  hydrochloride,  113,  114 
Benzylamine  nitrite,  114 
Benzylamines,  110 

Benzylamines,  amido-substituted,  116 
Benzylamines,  substitution  products  of, 

118 
Benzylammonium       benzylcarbamate, 

113,  114 

Benzylaniline,  117 
Benzyl,  arsenic  compounds  of,  125 
Benzyl  benzoate,  162 
Benzylbenzoyl  thio-urea,  179 
Benzyl  bromide,  97 
Benzyl  bromophenyl  ether,  95 
Benzyl  carbamate,  123 
Benzyl-carbimide,  122 
Benzyl  chloride,  7,  96 
Benzyl  chlorophenyl  ether,  95 
Benzylcyananmide,  121 
Benzylcyanuramide,  121 
Benzyl-Derivatives  of  the  Acid- Amides 

and  Allied  Bodies,  121 
Benzyldimethylselenine  tri-iodide,  110 
Benzyldimethylsulphine  iodide,  106 
Benzyl  dimethylsulphine  platinichlor- 

ide,  107 

Benzyl  dioxysulphide,  107 
Benzyl  diphenylamine,  117 
Benzyl  diselenide,  109 
Benzyl  disulphide,  107 
Benzyl,  ethereal  salts  of,  96 
Benzyl  ethers,  94 
Benzylethoxyl  chloride,  100 
Benzyl  ethyl  ether,  94 
Benzyl  ethyl  sulphide,  106 
Benzyl  group,  89 
Benzyl  hydrosulphide,  105 
Benzylhydroxyammomum  chloride,  98 
Benzyl  iodide,  97 
Benzyl-isocyanate,  122 
Benzyl  isocyanurate,  122 
Benzyl  isothiocyanate,  122 
Benzylmetamine,  121 
Benzyl  methyl  ether,  94 
Benzyl  mercaptan,  105 
Benzyl  mustard  oil,  122 
Benzyl  nitrate,  97 
Benzyl,  nitrogen  bases  of,  110 
Benzyl  orthocresyl  ether,  95 
Benzyl  oxalate,  98 
Benzyl  oxide,  94 
Benzyl  oxysulphide,  107 
Benzyl  paracresyl  ether,  95 
Benzylphenylamine,  117 
Benzyl   phenyldimethylammonium 

chloride,  117 
Benzyl  phenyl  ether,  95 


INDEX. 


527 


Benzylphosphine,  124 

Benzylphosphonium  iodide,  124 

Benzylquinol,  96 

Benzylsalicylic  acid,  306 

Benzyl  salicylaldehyde,  287 

Benzylselenic  acid,  109 

Benzyl  selenide,  109 

Benzyl,  selenium  compounds  of,  109 

Benzyl  selenocyanate,  123 

Benzyl,  silicon  compounds  of,  127 

Benzyl  sulphide,  106 

Benzylsulphonamide,  109 

Benzylsulphonic  acid,  108 

Benzylsulphonic  chloride,  108 

Benzyl,  sulphur  compounds  of,  105 

Benzyl  thiocarbamide,  124 

Benzyl  thiocyanate,  122 

Benzyl  thiobenzoate,  171 

Benzyl  urea,  123 

Benzyl  urethane,  123 

Beta-orcinol,  402 

Boron  and  Silicon  derivatives  of  Tolu- 
ene, 87 

Boron  disalicylic  acid,  304 

Bromamidobenzoic  acids,  255 

Bromanisic  acid,  336 

Bromine  substitution  products,  41 

Bromine  substitution  products  of  tolu- 
ene, 10 

Bromobeuzidenedichlorochromyl  chlo  • 
ride,  11 

Bromobenzylbenzoate,  170 

Bromogallic  acid,  370 

Bromomalophthalic  acid,  470 

Bromomeconin,  500 

Bromometacresol,  27 

a-Bromometatoluic  acid,  417 

j8-Bromometatoluic  acid,  417 

o-Bromometaxylene,  394 

s-Bromometaxylene,  394 

a-Bromometaxylenol,  401 

Bromonitrobenzoic  acids,  236 

Bromonitro  toluenes,  19 

Bromoparacresol,  29 

Bromoparahydvoxybenzaldehyde,  296 

o-Bromoparatoluic  acid,  420 

/J-Bromoparatoluic  acid,  420 

Bromoparaxylene,  395 

o-Bromophthalic  acid,  472 

v-Bromophthalic  acid,  472 

Bromopianic  acid,  507 

Bromoprotocatechuic  acid,  356 

a-Bromoresorcylic  acid,  359 

7-Bromoresorcylic  acid,  361 

Bromorthocresol,  25 

a-Bromorthotoluic  acid,  415 

j8-Bromorthotoluic  acid,  415 

o-Bromorthoxylene,  393 

Bromosalicylaldehyde,  292 

a-Bromosalicylic  acid,  314 

0-Bromosalicylic  acid,  314 

Bromosulphobenzoic  acids,  274 

Bromoterephthalic  acid,  488 
Bromotoluidines,  68 


Butyl  benzoate,  162 
Butyl  hippurate,  191 


C. 

CAFFEOL,  281 

Calcium  benzarsenite,  278 

Calcium  benzoate,  160 

Calcium  dibenzarsenite,  278 

Calcium  difluorbenzoate,  227 

Calcium  gallate,  369 

Calcium  hippurate,  189 

Calcium  isophthalate,  479 

Calcium  metachlorobenzoate,  220 

Calcium  metahydroxybenzoate,  321 

Calcium  metatoluate,  416 

Calcium  ornithurate,  193 

Calcium  orthochlorobenzoate,  218 

Calcium  orthotoluate,  414 

Calcium  parachlorobenzoate,  221 

Calcium  parahydroxybenzoate,  328 

Calcium  paratoluate,  419 

Calcium  phthalate,  457 

Calcium  piperonate,  356 

Calcium  pyrogallolcarboxylate,  379 

Calcium  quinate,  382,  384 

Calcium  salicylate,  303 

Calcium  terephthalate,  484 

Cantharene,  391 

Carbanilamide,  246 

Carbanilidic  acid,  246 

Carbimidamidobenzoic  acid,  250 

Carbimidamidobenzoyl,  242 

Carbohydrokinonic  acid,  350 

Carbonyl  chloride,  462 

Carbonyl  dibenzenylamidoxime,  215 

Carbotriphenyltriamine,  204 

Carboxamidocyanamidobenzoyl,  241 

Carboxamidobenzoic  acid,  251 

Carboxylcyanamidobenzoyl,  241 

Catechol,  36 

Chloranisic  acid,  336 

Chloramidobenzoic  acids,  254 

Chlorine  substitution  products,  41 

Chlorine    substitution     products      of 

toluene,  7 
Chlorobenzol,  136 
Chlorobenzoyl  chloride,  310 
Chlorobenzenyl  trichloride,  310 
Chlorodracylic  acid,  221 
Chloro-isophthalic  acid,  481 
Chloromeconin,  500 
Chlorometatoluic  acid,  417 
Chlorometaxylenesulphamide,  393 
Chloromethylnoropianic  acid,  503 
o-Chlorometaxylene,  393 
Chloromichmic  acid,  219 
Chloroniceinic  acid,  219 
Chloronitrotoluenes,  19 
Chloronitrobenzoic  acids,  236 
Chloroparacresol,  29 
Chloroparahydroxybenzaldehyde,  296 
Chloroparahydroxybenzoic  acid,  334 
Chloroparatoluic  acid,  420 


528 


INDEX. 


Chloroparatoluidiue,  8 

Chlorophthalic  acid,  393 

o-Chlorophthalic  acid,  471 

•y-Chlorophthalic  acid,  471 

Chloroparaxylene,  393 

Chloropiauic  acid,  507 

Chlororthotoluic  acids,  415  - 

a-Chlororthoxylene,  392 

•y-Chlororthoxylene,  392 

Chlorosalicylaldehyde,  292 

Chlorosalicylic  acid,  313 

Chlorosulphobenzoic  acids,  274 

Chlorotorephthalic  acid,  488 

Chlorotoluene,  7 

Chlorotoluic  acid,  393 

Chlorotoluidines,  68 

Choline,  376 

Cinnamei'n,  90 

Cinnaraic  acid,  90,  135,  297 

Cinnamone,  135 

Colophonin  hydrate,  7 

Colophonin,  6 

Coniferyl  alcohol,  345 

Copper  benzoate,  161 

Copper  hippuratc,  190 

Copper  metahydroxybenzoate,  321 

Copper  parahj-droxybenzoate,  328 

Copper  phthalate,  457 

Copper  quinate,  384 

Copper  salicylaldehyde,  287 

Copper  salicylate,  304 

Couraaim,  186 

Creosol,  32 

Creosote,  32  et  seq. 

o-Cresol,  23 

j8-Cresol,  23 

7-Cresol  24 

Cresolcarboxylic  acid,  438 

Cresorcinol,  47,  437 

Cresorcinolcarboxylic  acid,  437 

Cresorsellinic  acid,  437 

Cresotic  acid,  423 

a-Cresotic  acid,  423 

fi-Cresotic  acid,  424 

7-Cresotic  acid,  424 

Cresyl  alcohol,  23 

Cresyl  benzoate,  164 

Cresyl  hydrate,  23 

Cudbear,  44 

Cumaric  acid,  297 

Cumic  acid,  451 

Cumino-cyminic  acid,  451 

Cumol,  386 

Cyanobenzylamine,  121 

Cyanocarbimidobcnzoic  acid,  249 

Cyanocarboxamidobenzoic  acid,  249 

Cynanphenin,  199 

Cymene,  4 

Cymol,  386 


DlACETORTHO-AMIDOBENZOIC  ACID,  239 

Diacetotoluquinol,  48 
Diamidobenzoic  acids,  258 


Diamidobenzoic  acids,  action  of  nitrous 

acid  on  the,  263 
a-Diamidobenzoic  acid,  258 
/}-Diamidobenzoic  acid,  259 
5 -Diamidobenzoic  acid,  267 
7-Diamidobenzoic  acid,  259 
8  Diamidobenzoic  acid,  259 
5-Diamidobenzoic  acid  hydrochloride, 

259 

5-Diamidobenzoic  acid  sulphate,  259 
Diamidobenzylsulphonic  acid,  109 
Diamidocresol,  79 
Diamidohydro-acridine  ketone,  245 
o-Diamidometaxylene,  409 
T-Diamidometaxylene,  409 
s-Diamidometaxylene,  409 
o-Diamidoparaxylene,  410 
£-Diamidoparaxylene,  410 
7-Diamidoparaxylene,  410 
Diamidosalicylic  acid,  318 
Diamidoterephthalic  acid,  489 
a-Diamidotoluene,  72 
/3-Diamidotoluene,  72 
7-Diamidotoluene,  73 
5-Diamidotoluene,  74 
a-Diamidotoluene  di-hydrochloride,   72 
£-Diamidotoluene  hydrochloride,  73 
7-Diamidotoluene  hydrochloride,  73 
a-Diamidotoluene  monohydrochloride, 

72 

a-Diamidotoluene  sulphate,  72 
£-Diamidotoluene  sulphate,  73 

S-Diamidotoluene  sulphate,  73 
iamidotoluenes,  72 
Diamidotriphenylmethane,  135 
Diamines     and     Thamines    of   the 

Xylenes,  409 
Dianilidotoluquinone,  49 
Dianilidotoluquinone  anilide,  49 
Dianisbenzhydroxylamine,  342 
Dianishydroxamic  acid,  340 
Diazo-amidobenzene,  18 
Diazo-amidotoluene,  74 
Diazo-amidotoluic  acid,  421 
Diazobenzene-amidobenzoic  acid,  262 
Diazobenzoic  acid,  260 
Diazobenzoic  acid  nitrate,  260 
Diazobenzoic  acid  seminitrate,  260 
Diazo-derivatives  of  benzoic  acid,  260 
Diazo-derivatives  of  toluene,  74 
Diazohemipinic  acid,  513 
Diazo-imidobenzoic  acids,  263 
Diazooenzene-amidotoluene,  74 
Diazo-salicylic  acid,  319 
Diazotoluene  nitrate,  74 
Diazotoluene  sulphate,  74 
Diazoxybenzoic  acid,  267 
Dibenzamide,  176 
Dibenzamide  hydrate,  177 
Dibenzanilide,  177  . 
Dibenzanishhydroxylamine,  341 
Dibenzarsene  iodide,  278 
Dibenzarsenic  acid,  278 
Dibenzarsenious  acid,  278 


INDEX. 


529 


Dibenzenylazoxime,  214 
Dibenzenyltriamine,  202 
Dibenzhydroxamic  acid,  209 
Dibenzhydroxylamine,  207 
Dibenzidenediumidobenzoic  acid,  142 
Dibeuzidenemetadiamidotoluene,  142 
Dibenzidene-orthodiamidotoluene,  1 42 
Dibenziiaido-oxide,  197 
Dibenzoarsenic  acid,  85 
Dibenzobenzoximate,  211 
Dibenzoylcatechol,  164 
Dibenzoylphenylhydrazinc,  180 
Dibenzoylquinol,  164 
Dibenzoylrescorciuol,  164 
Dibenzoyl  urea,  179 
Dibenzenylamidine,  202 
Dibenzylamine,  114 
Dibenzylamine  hydrochloride,  115 
Dibenzylamine  nitrate,  115 
Dibenzylarsenic  acid,  126 
Dibenzylarsine  trichloride,  125 
Dibenzylcatechol,  96 
Dibenzylcyanimide,  122 
Dibenzyl  ether,  94 
Dibenzylguanidine,  121 
Dibenzyloxamide,  121 
Dibenzylphosphine,  125 
Dibenzylquinol,  96 
Dibenzylresorcinol,  96 
Dibenzyl  sul phone,  107 
Dibenzyltolylamine,  118 
Dibenzyl  toluidine,  118 
Dibromanisic  acid,  336 
Dibromobenzoic  acids,  224 
Dibromo-gallic  acid,  370 
Dibromohexhydroterephthalic      acid, 

486 

Dibromolecanoric  acid,  434 
o-Dibromometaxylene,  394 
/3-Dibromometaxylene,  394 
a-Dibromometaxylenol,  401 
Dibronioparacresol,  29 
Dibromoparahydroxybenzoic  acid, 

334 

Dibromoparatoluic  acid,  420 
Dibromoparaxylene,  395 
o-Dibromophtnalic  acid,  472 
#-Dibromophlhalic  acid,  473 
Dibromophthalide,  444 
Dibromorcinol,  41 
Dibromorsellinic  acid,  433 
Dibromorthoxylene,  solid,  394 

liquid,  394 

Dibromoterephthalic  acid,  488 
Dibromotoluenes,  11 
Dibromotetrahydrophthalic  acid,  470 
Dichloraniaic  acid,  336 
Dichlorobenzaldehyde,  144 
Dichlorobenzenyl  trichloride,  196 
o-Dichlorobenzoic  acid,  221 
/3-Dichlorobenzoic  acid,  222 
7-Dichlorobenzoic  acid,  222 
S-Dichlorobenzoic  acid,  222 
e-Dichlorobenzoic  acid,  222 


Dichlorobenzidene  chloride,  145 
Dichlorobenzoic  acids,  221 
Dichlorobenzyl  alcohol,  100 
Dichlorobenzyl  chloride,  101 
Dichlorohippuric  acid,  220 
Dichloroparacresol,  29 
Dichloroparahydroxybenzoic  acid,  334 
Dichloroparaxylene,  393 
Dichlorophthalic  acid,  471 
Dichloropiperonal,  348 
Dichlororthocresol,  25 
Dichlororthoxylene,  393 
Dichloro-salicylic  acid,  314 
Dichlorosilicon  orthoditoluide,  87 
Dichlorotoluene  hexchloride,  10 
Dichlorotoluenes,  9 
Dichlorotoluquinone,  27,  50 
Dicinnyl  ketone,  135 
Dicyanamidobenzoyl,  241 
Diethylbenzamide,  174 
Diethylbenzylamine,  116 
Diethyl  diacetoxyterephthalate,  517 
Diethyldiamidoterephthalate,  489 
Diethyldibenzylammonium  iodide,  117 
Diethyl  o-hydroxyisophthalate,  495 
Diethyl  s-hydroxyisophthalate,  495 
Diethyl  dihydroxyterephthalate,  516 
Diethylorthotoluidine,  59 
Diethylparadihydroxybenzaldehyde, 

349 

Di-ethylparatoluidine,  65 
Diethylprotocatechuic  acid,  355 
Diethyl-/3-resorcylaldehyde,  349 
Diethyl-a-resorcylic  acid,  359 
Diethyl-£-resorcylic  acid,  360 
Difluorbenzoic  acid,  227 
Digallic  acid,  371 
Dihydro-orthoxylene,  391 
Dihydrophthalic  acid,  469,  487 
Dihydrotoluene,  6 
Dihydroxybenzoic  acids,  350 
Dihydroxybenzyl      and      Dihydroxy- 

Benzoyl  compounds,  343 
Dihydroxyhexhydroterephthalic    acid, 

487 

Dihydroxyisophthalaldehyde,  515 
Dihydroxyisophthalic  acid,  515 
Dihydroxyphthalic  acids,  510 
Dihydroxyquinone,  520 
Dihydroxyterephthalic  acid,  515 
Dihydroxytoluenes  and  allied  bodies, 

31 

Dihydroxytolualdehydes,  427 
Dihydroxytoluic  acids,  428 
Dihydroxytoluquinone,  49 
Dihydroxy-xylenes,  402 
Di-iodoparacresol,  29 
Di-iodoparahydroxy  ben  zoic  acid,  335 
Di-iodosalicylic  acid,  315 
Dimetatolyl  carbamide,  63 
Dimetatolyl  thiocarbamide,  63 
Dimethoxybenzonitril,  361 
Dimethoxyorthophthalic  acid,  510 
Dimethyl  acetoxyterephthlate,  496 


530 


INDEX. 


Dimethylamidophenylhydroxytri- 

chlorethane,  151 
Dimethylbenzamide,  174 
Dimethylbenzenes,  390 
Dimethyldiamidotoluene,  62 
Dimethyldihydroxyphthalic  acid,  498 
Dimethyl  a-hydroxyisophthalate,  495 
Dimethyl  s-hydroxyisophthalate,  495 
Dimethylhydroxysalicylic  acid,  362 
Dimethyl  hydroxyterephthalate,  496 
Dimethylmetamidobenzoic  acid,  247 
Dimethylmetatoluidine,  61 
Dimethylmethylene  benzoate,  163 
Dimethylnoropianic  acid,  503 
Dhnethylorthotoluidine,  58 
Dimethylparadihydroxybenzaldehyde, 

349 

Dimethylparamidobenzaldehyde,  1 50 
Dimethylparamidobenzoic  acid,  253 
Dime  thy  Iparatolui  dine,  65 
Dimethylparatolyl  phosphine,  84 
Dimethyltolylphosphine  oxide,  84 
Dimethylphenylenebenzenylamide  am- 
monium iodide,  205 
Dimethylphosphine-oxide  benzoic  acid, 

277 

Dimethylprotocatechuic  acid,  354 
Dimethylprotocatechuicaldehyde,  346 
Dimethyl-£-resorcylaldehyde,  349 
Dimethyl-o-resorcylic  acid,  358 
Dimethyl-/3-resorcylic  acid,  360 
Dimethyl-7-resorcylic  acid,  361 
Dinitro-amidobenzoic  acids,  257 
Dinitro-anisic  acid.  337 
Dinitro-anthranilic  acid,  257 
o-Dinitrobenzoic  acid,  234 
£-Dinitrobenzoic  acid,  234 
7-Dinitrobenzoic  acid,  234 
8-Dinitrobenzoic  acid,  235 
e-Dinitrobenzoic  acid,  235 
Dinitrobenzoic  acids,  234 
Dinitrobenzysulphonic  acid,  109 
Dinitro-diphenylamine-orthocarboxylic 

acid,  245 

Dinitro-i?-hydroxyphthalic  acid,  493 
Dinitrohydroxyterephthalic  acid,  496 
s-Dinitrometaxylene,  396 
r-Dinitrometaxylene,  396 
o-Dinitro-orcinol,  41 
£-Dinitro-orcinol,  42 
Dinitro-ortharnidobenzoic  acid,  257 
Dinitro-orthocresol,  26 
a-Dinitro-orthotoluiuine,  71 
Dinitro-orthoxylene,  396 
Dinitroparacresol,  30 
Dinitroparahydroxybenzoic  acid,  335 
Dinitroparamidobenzoic  acid,  258 
Dinitroparaxylidine,  408 
o-Dinitroparaxylene,  397 
£-Dinitropaiaxylene,  397 
7-Dinitroparaxylene,  397 
Dinitrophthalic  acid,  475 
Dinitrosalicylic  acid,  317 
7-Dinitrotoluene,  17 


Dinitrotoluene,     ordinary,     16 ;    sym- 
metric, 17 
Dinitrotoluenes,  16 
Dinitrotoluidine,  18 
£-Dinitrotoluidine,  71 

S Dinitrotoluidine,  71 
initrotoluidines,  71 
7-Dinitrotolylphenylamine,  18 
Diorsellinic  acid,  433 
Di-orthotolylamine,  59 
Di-orthotolylcarbamide,  59 
Di-orthotolyl  thiocarbamide,  60 
Diparahydroxybenzoylparahydroxy- 

benzoic  acid,  331 
Diparatolylamine,  66 
Diparatolylarsenic  acid,  85 
Diparatolyl  carbamide,  66 
Diparatolylhydrazine,  75 
Diparatolylnitrosamine,  66 
Diparatolyl  thiocarbamide,  67 
Diphenylbenzene,  452 
Diphenylbenzenylamidine,  204 
Diphenylorthoxylylenediamine,  440 
Diphenylparamidobenzenylamidine,204 
Diphenylphthalamic  acid,  465 
Diphenylphthalei'n,  465 
Diphenylthiobenzamide,  178 
Diphthalyl,  458,  460 
Disalicylamide,  312 
Disalicylic  acid,  308 
o-Disulphobenzoic  acid,  274 
£-Disulphobenzoic  acid,  274 
Disulphobenzoic  acids,  274 
Disulphometahydroxy  benzoic  acid,  326 
Disulphorthotoluic  acid,  416 
Dithiobenzoic  acid,  172 
Dithiometahydroxybenzoic  acid,  325 
Dixylylainine,  412 
Dragonic  acid,  329 
Drupacese,  131 


E. 


ERYTHRELINIC  ACID,  429 

Erythric  acid,  429 

Erythrinbitter,  428 

Erythrylin,  428 

Erythrin,  428,  431,  434 

j8-Erythrin,  435 

Erythroglucin,  430 

Ethereal  salts  of  Benzyl,  96 

Ethereal  salts  of  salicylic  acid,  306 

Ethereal  salts  of  salicylic  ethers,  307 

Ethers  of  benzoic  acid,  160 

Ethers  of  benzyl  with  the  dihydroxy- 

benzenes,  95 

Ethers  of  phthalic  acid,  457 
Ethidenedibenzamide,  176 
Ethoxycarbimidamidcbenzoic  acid,  250 
Ethoxycyanamidobenzoyl,  242 
Ethoxymethoxybenzonitril,  361 
Ethoxynitrobenzonitril,  361 
Ethyl  amido-isophthalate,  482 


INDEX. 


531 


Ethyl  a-amidophthalate,  476 
k  Ethyl  iJ-amidophthalate,  475 
'Ethyl  anisbenzhydroxamate,  340 
Ethyl  anishydroxamate,  339 
Ethylanishydroxamic  acid,  339 
o-Ethylbenzanishydroxamate,  340 
£-Ethylbenzanishydroxamate,  340 
Ethyl    benzenylamidoximecarboxylate, 

214 

Ethenylbenzenylazoxime,  214 
a-Ethylbenzhydroxamic  acid,  211 
Ethyl  benzhydroxamate,  209 
Ethyl  benzoate,  161 
Ethyl  benzoyl-glycollate,  165 
Ethyl  benzoyl-lactate,  165 
Ethylbenzoyl  thio-urea,  179 
Ethyl-benzylamidine,  202 
Ethylbromosalicylaldehyde,  292 
Ethyleue  benzoate,  162 
Ethyl-#-diamidotoluene,  73 
o-Ethyl  dibenzhydroxaraate,  210 
£-Ethyl  dibenzhydroxamate,  210 
Ethyl  dibenzylamine,  117 
Ethyl  dibromoterephthalate,  488 
Ethyl  dihydroxyquinoneterephthalate, 

519 

Ethylenebenzamide,  174 
Ethyleneprotocatechuic  acid,  356 
Ethylene  salicylate,  306 
Ethylene  salicylic  acid,  306 
Ethyl  ether  of  benzenylamidoxime,  213 
Ethyl  ethylenesalicylate,  307 
Ethyl  ethylsalicylate,  307 
Ethyl  gallate,  369 
Ethyl  hemipinimide,  514 
Ethyl  hippurate,  190 
j8-Ethylhydroxamic  acid,  211 
Ethyl  hydroxysalicylate,  362 
Ethyl  isophthalate,  479 
Ethyl  metacyanobenzoate,  480 
Ethyl  meta-ethoxybenzoate,  322 
Ethyl  metahydroxybenzoate,  321 
Ethyl  metanitrobenzoate,  231 
Ethyl  metasulphamidobenzoate,  272 
Ethyl  metasulphobenzoic  acid,  271 
Ethyl  metatoluate,  417 
Ethyl  methylsalicylate,  307 
Ethyl  nitro-isophthalate,  482 
Ethylnitrolic  acid,  468 
Ethyl  opianate,  505 
Ethyl  orsellinate,  433 
Ethyl  orthobenzoate,  194 
Ethyl  orthocyanobenzoate,  468 
Ethyl  orthonitrobenzoate,  230 
Ethyl  orthotoluate,  414 
Ethylorthotoluidine,  59 
Ethyl  paracyanobenzoate,  485 
Ethylparadihydroxybenzaldehyde,  349 
Ethyl  para-ethoxybenzoate,  330 
Ethyl  parahydroxybenzoate.  330 
Ethyl  paramethoxybenzoate,  330 
Ethyl  paranitrobenzoate,  232 
Ethyl  paratoluate,  419 
Ethylparatoluidine,  65 


Ethyl  phthalate,  457 

Ethyl  phthalimide,  464 

Ethylphthalylhydroxylamine,  467 

Ethyl  piperonate,  356 

Ethyl  pyro-gallolcarboxylate,  379 

Ethyl  quinate,  385 

Ethyl  a-resorcylate,  358 

Ethyl  salicylaldehyde,  287 

Ethyl  salicylate,  306 

Ethyl  terephthalate,  484 

Ethyl  tetracetylquinate,  385 

Ethyl  tetrachlorophthalate,  472 

Ethyl  tetrahydroxyterephthalate,  520 

Ethyl  thiobenzoate,  171 

Ethyltolyl  carbamate,  67 

Ethylvanillic  acid,  355 

Ethyl  veratrate,  355 

Ethysalicylic  acid,  306 

Evernic  acid,  435 

Everninic  acid,  435 


P. 


FEKRIC  benzoate,  161 

Fluorine    substitution    products    of 

toluene,   13 

Formortho-arnidobenzoic  acid,  239 
Fluotoluene,  13 


G. 

GALLAMIDE,  370  • 
Gallates,  the,  368 
Gallic  acid,  363,  381 
Gallocarboxylic  acid,  519 
Gallocyanin,  377 
Gentisic  acid,  362 
Gentisinaldehyde,  349 
Glucovanillic  acid,  352 
Glucovanillin,  347 
Glucovanillyl  alcohol,  347 
Guanidodibenzoic  acid,  260 


H. 


HALOGEN  compounds  of  benzoyl,  168 
Halogen  substitution  products,  118 
Halogen    substitution    products    of 

benzoic  acid,  216 
Halogen    substitution    products    of 

phthalic  acid,  471 
Halogen    substitution    products    of 

the  Toluidines,  67 
Halogen    substitution    products    of 

the  Xylenes,  392 
Helicin,  288 
Helicoi'din,  289 
Hemipinic  acid,  497,  510 
Hemipinic  anhydride,  511 
Hemipinimide,  513 
Hemipinimidine,  501 


532 


INDEX. 


Heptacarbure  quadrihydrique,  3 
Hexbromobenzene,  12 
Hexchloroxylone,  34 
Hexhydrometaxylene,  391 
Hexhydroparaxylene,  392 
Hexhydrophthalic  acid,  470 
Hexhydroterephthalic  acid,  486 
Hexhydrotoluene,  7 
Hexmethyl-5-diamidobenzoic  acid,  259 
Hexnitrodiparatolylamine,  66 
Hipparin,  175 
Hippuramide,  191 
Hippuramido-acetic  acid,  191 
Hippurates,  the,  189 
Hippurglycollamide,  192 
Hippuric  acid,   181,  383  ;  properties, 

188 

Homocatechol,  31 
Homocatechol  dimethyl  ether,  32 
Homocatechol  monomethyl  ether,  32 
Homo-erythrin,  435 
Homohydroxysalicylic  acid,  438 
Homopyrocatechin,  31 
Homorcinol,  402 
Homosalicylic  acids,  423 
Homosaligenin,  422 
Hydrazenebenzoic  acids,  264 
Hydrazine-derivatives  of  Toluene,  75 
Hydrazobenzoic  acids,  265 
o-Hydrazotoiuidine,  79 
0-Hydrazotoluidine,  79 
Hydrobenzamide,  139,  140 
Hydrobenzamide  trijldehyde,  449 
Hydrobenzamidetricarboxylic  acid,  449 
Hydrobenzoic  acid,  159 
Hydrobenzuric  acid,  192 
Hydrobenzyluric  acid,  192 
Hydro phlorone,  403 
Hydrophthalide,  444 
Hydrosalicylamide,  291 
Hydroxybenzaldehydes,  285 
Hyd roxybenzidene-amidobenzoic  acid, 

291 

Hydroxybenzoic  acids,  297 
Hydroxybenzyl  alcohols,  279 
Hydroxybenzyl  group,  279 
Hydroxybcnzyluric  acid,  192 
o-Hydroxyisophthalic  acid,  494 
s-Hydroxyisophthalic  acid,  495 
v-Hydroxyisophthalic  acid,  495 
Hydroxyisophthalic  acid,  303 
Hydroxylamine  derivatives  containing 

three  acid  radicals,  341 
Hydroxymetaxyloquinone,  404 
Hydroxymethylbenzoic  acids,  442 
Hydroxymethyldihydroxybenzoic 

acids,  497 
Hydroxymethyldimethoxybenzoic 

acid,  500 
Hydroxymethylhydroxybenzoic  acid, 

490 

v-Hydroxyorthophthalic  acid,  493 
Hydroxyphthalamic  acid,  467 
o-Hydroxyphthalic  acid,  492 


Hydroxyphthalic  acids,  492 
o-Hydroxyphthalic  anhydride,  493 
Hydroxyquinolcarboxylic  acid,  380, 

381 

Hydroxysalicylic  acid,  361 
Hydroxyterephthalic  acid,  495 
Hydroxytolualdehydes,  422 
s-Hydroxytoluic  acid,  425 
Hydroxytoluic  acids,  423 
Hydroxytoluquinonoxime,  52 
Hydroxytrinesic  acid,  303,  494 
Hydroxy-xylenes,  399 
Hypogallic  acid,  498 


I. 


IMIDE  of  metadiazobenzoic  acid,  264 
Insolinic  acid,  451 
lodamidobenzoic  acids,  255 
lodanisic  acid,  337 
Iodine  substitution  products,  41 
Iodine    substitution    products    of 

Toluene,  13 

lodo-isophthalic  acid,  481 
lodomeconin,  500 
lodometahydroxybenzoic  acid,  323 
lodonitrobenzoic  acids,  237 
lodoparacresol,  29 
lodoparahydroxybenzaldehyde,  296 
lodoparahydroxybenzoic  acid,  335 
lodoparatoluic  acid,  420 
lodosalicylic  acid,  314 
lodotoluenedisul  phonic  acid,  22 
lodotoluidines,  68 
Iron  gallate,  369 
Jsobutyl  hippurate,  191 
Isobutyl  terephtlmlate,  484 
Isodiazoxybenzoic  acid,  267 
Isohemipinic  acid,  515 
Isonitrosobenzyl  ether,  98 
Isonoropianic  acid,  508 
Isophthalalcohol,  440 
Isophthalaldehyde,  447 
Isophthalic  acid,  451,  479 
Isophthalic  acid,  addition  products  of, 

481 
Isophthalic  acid,  substitution  products 

of,  481 

Isophthalamide,  480 
Isophthalonitril,  481 
Isophthalyl  chloride,  480 
Isopianic  acid,  509 
Isopropyl  benzoate,  162 
Isopropylsalicylic  acid,  306 
Isopropyl  terephthalate,  484 
Isorcinol,  47 
Isosulphometahydroxybenzoic   acid, 

325 

Isotrichloroglyceric  acid,  368 
Isovanillic  acid,  353 
Isovanillin,  346 
Isoxylol,  387 


INDEX. 


533 


J. 
JUGLONIC  acid,  493 


K. 


KINOIN,  374 
Kino-red,  374 


LEAD  benzoate,  161 

Lead  benzyl  mercaptide,  106 

Lead  benzylsulphonate,  108 

Lead  dithiobenzoate,  172 

Lead  gallate,  369 

Lead  hippurate,  190 

Lead  opianate,  504 

Lead  opianylsulphite,  507 

Lead  parahydroxy benzoate,  328 

Lead  phthalate,  457 

Lead  proto-catechuate,  352 

Lead  quinate,  384 

Lead  salicylaldehyde,  287 

Lead  salicylate,  304 

Lecanoric  acid,  429,  432,  433 

Lecanorin,  429 

Lithium  salicylate,  303 

Litmus,  45 

Luteolin,  357 


M. 

MACLTTRIN,  356 
Magnesium  hippurate,  189 
Maluchite-green,  135 
Mandelic  acid,  131 
Meconin,  497,  500 
^-Meconin,  501 
Meconinic  acid,  500 
Meconiosin,  502 
Menyanthin,  423 
Menyanthol,  423 
Mercuric  benzamide,  174 
Mercuric  benzoate,  161 
Mercury  benzyl  mercaptide,  105 
Mercury  derivatives  of  Toluene,  87 
Mercury  orthotolyl,  88 
Mercury  paratolyl,  88 
Meta-acetobenzyl  acetate,  283 
Meta-acetoxybenzoic  acid,  322 
Meta-azotoluene,  76 
Meta-benzamoxalic  acid,  248,  249 
Metabenzenyltrichlorophosphoryl 

chloride,  322 
Metabenzobetaine,  248 
a-Metabenzo-creatine,  252 
£-Metabenzo-creatine,  252 
Metabenzoglycocyamine,  251 
Metabenzosarcosine,  247 
Metabromobenzaldehyde,  145 
Metabromobenzoic  acid,  223 
Metabromobenzyl  bromide,  102 


Metabromotoluene,  11 
Metacarbamidobenzoic  acid,  251 
Metacarbonylphenylphosphoryl 

chloride,  322 

Metacarboxyorthophosphoric  acid,  322 
Metachlorobenzaldehyde,  144 
Metachlorobenzoic  acid,  219 
Metachlorobenzonitril,  220 
Metachlorobenzoyl  chloride,  220,  383 
Metachlorohippuric  acid,  220 
Metachlorotoluene,  8 
Metacresol,  24,  27 
Metacresyl  benzoate,  164 
Metacresyl  oxide,  27 
Metacyanobenzoic  acid,  480 
Metadiamidobenzylarnine,  1 20 
Metadiazo-amidobenzoic  acid,  262 
Metadiazobenzamide  nitrate,  261 
Metadiazobenzoic  acid,  261 
Metadiazobenzoic  acid  imide,  264 
Metadiazobenzoic  acid  nitrate,  261 
Metadiazobenzoic  acid  perbromide, 

261 
Metadiazobenzoic  acid  platinichloride, 

261 

Metadiazobenzoic  acid  sulphate,  261 
Metadiazobenzonitril  nitrate,  262 
Metadihydroxybenzaldehyde,  348 
Metadinitrobenzylamine,  119 
Metadithiobenzoic  acid,  272 
Metaditolylamine,  62 
Meta-ethoxybenzoic  acid,  322 
Metafluorbenzoic  acid,  226 
Metafluorhippuric  acid,  226 
Metaguanidobenzoic  acid,  251 
Metahomometahydroxybenzoic  acid, 

425 
Metahomomethoxycalicylaldehyde, 

acid,  428 
Metahomoparahydroxybenzaldehyde, 

422 
Metahomoparahydroxybenzoic  acid, 

426 

Metahomosalicylaldehyde,  422 
a-Metahomosalicylic  acid,  424 
/3-Metahomosalicylic  acid,  424 
Metahydrazinebenzoic  acid,  264 
Metahydrazobenzoic  acid,  266 
Metahydrazotoluene,  76 
Metahydroxybenzaldehyde,  293 
Metahydroxybenzamide,  323 
Metahydroxybenzanilide,  323 
Metahydroxybenzenylamidoxime, 

216 

Metahydroxybenzoates,  320 
Metahydroxybenzoic  acid,  substitution 

products  of,  323 
Metahydroxybenzonitril,  323 
Metahydroxybenzoic  acid,  320 
Metahydroxybenzoylsulphuric  acid, 

326 

Metahydroxybenzuric  acid,  323 
Metahydroxybenzyl  acetate,  283 
Metahydroxybenzyl  alcohol,  283 


205 


534 


INDEX. 


Metahydroxybenzyl  diacetate,  283 
Metahydroxyovthotoluic  acid,  425 
Metahydroxyparatoluic  acid,  426 
Meta-iodobenzoic  acid,  225 
Meta-iodotoluene,  13 
Metamethoxybenzoic  acid,  321 
Metamethoxysalicylaldehyde,  349 
#-Metamethoxysalicylaldehyde,  348 
Metamidobenzaldoxime,  150 
Metamidobenzaldehyde,  150 
Metamidobenzamide,  247 
Metamidobenzenylamidoxime,  216 
Metamidobenzoic  acid,  246,  248,  252 
Metamidobenzoic  acid  hydrochloride, 

247 

Metamidobenzonitril,  247 
Metamidobenzylphenylamine,  120 
Metamidoparamethyltoluidine,  73 
Metamidoparazotoluene,  78 
Metanitrobenzaldehyde,  147 
Metanitrobenzaldoxime,  147 
Metanitrobenzamide,  231 
Metanitrobenzenylamidoxime,  216 
Metanitrobenzidene  bromide,  147 
Metanitrobenzidene  chloride,  147 
Metanitrobenzoic,  230 
Metanitrobenzoic  acid,  228 
Metanitrobeuzonitril,  232 
Metanitrobenzoyl  chloride,  231 
Metanitrobenzyl  alcohol,  104 
Metanitrobenzylamine,  119 
Metanitrobenzylamines,  119 
Metanitrobenzyl  chloride,  104 
Metanitrobenzylphenylamine,  119 
Metanitrohippuric  acid,  232 
Metanitromethylmetahydroxybenzalde- 

hyde,  294 

Metanitro-orthotoluidine,  69 
Metanitropara-ethyltoluidine,  71 
Metanitroparamethyltoluidine,  7 1 
Metanitroparatoluidine,  70 
Metanitrotoluene,  16 
Metaphlorone,  404 
Metaphthalic  acid,  479 
Metasulphamidobenzoic  acid,  272 
Metasulphamido-orthotoluic  acid,  416 
Metasulphobenzamide,  271 
Metasulphobenzoates,  270 
Metasulphobenzoic  acid,  269 
Metasulphobenzoyl  chloride,  271 
Metathiocresol,  31 
Metathiohydrobenzoic  acid,  272 
Metatoluaidehyde,  413 
Metatoluic  acid,  416 
Metatoluidine,  60 
Metatoluidine  hydrochloride,  61 
Metatoluidine  nitrate,  61 
Metatoluidine  sulphate,  61 
Metatolunitril,  417 
Metatoluyl  chloride,  417 
Metatoluylenediamine,  72 
Metatolyl  carliamide,  63 
Metatolyl  mustard  oil,  63 
Metatolylstibine,  86 


Metatolyl  thiocarbamide,  63 
Metatriamidobenzylamine,  120 
Metatrinitrobenzy  lamine,  1 1 9 
Meta-uramidobenzoic  acid,  250 
Meta-urethanebenzoic  acid,  251 
Metaxylene,  388,  389,  391 
a-Metaxylenesulphamide,  399 
a-Metaxylenesulphonic  acid,  398 
v-Metaxylenesul  phonic  acid,  399 
o-Metaxylenesulphonic  chloride,  398 
o-Metaxylenol,  400 
s-Metaxylenol,  401 
w-Metaxylenol,  401 
o-Metaxylenyl  acetate,  401 
Metaxylidenehydrazine,  413 
Metaxylidene  tetrachloride,  447 
Metaxylylene  alcohol,  440 
Metaxylylene  bromide,  441 
Metaxylylene  chloride,  441 
Metaxylylene  ethyl  ether,  440 
o-Metaxylenyl  methyl  ether,  400 
o-Metaxylidine,  406 
s-Metaxylidine,  407 
u-Metaxylidine,  406 
Metazobenzoic  acid,  266 
Metazoxybenzoic  acid,  266 
Methenylamidorthocresol,  26 
MetAxyloquinol,  403 
Metaxyloquinone,  404 
Metaxylorcinol,  402 
Metaxylyl  acetate,  412 
Metaxylyl  alcohol,  411 
Metaxylyl  bromide,  412 
Metaxylyl  chloride,  412 
Metaxylyl  ethyl  ether,  411 
o-Methoxyisophthalic  acid,  494 
u-Methoxyisophthalic  acid,  495 
Methoxynitrobenzonitril,  361 
Methoxyterephthalic  acid,  496 
Methyl  aldehydovanillate,  509 
Methyl  amido-anisate,  338 
Methylamido-anisic  acid,  338 
Methyl  amido-isophthalate,  482 
Methyl  amido-terephthalate,  489 
Methylbenzene,  3 
Methyl  benzoate,  161 
Methylbenzoylphenylhydrazine,  180 
Methylbenzyl,  387 
Methyl  benzyJsalicylate,  307 
Methylbromosalicylaldehyde,  292 
Methyl  bromoterephthalatc,  488 
Methyl  chloroterephthalate,  488 
Methylcinnyl  ketone,  135 
Methyl  cresolcarboxylate,  439 
Methyl-j8-diamidotoiuene,  73 
Methyldibenzoylphenylhydrazine,  1 80 
Methyl  dimethylamidosalicylate,  318 
Methylenedibenzamide,  175 
Methyleneprotocatechuicaldehyde,  347 
Methyl  ethylsalicylate,  307 
Methyl  hippurate,  190 
a-Methylhydroquinoneformic  acid,  362 
a-Methylhydroxyphthalic  acid,  493 
u-Methylhydroxyphthalic  acid,  493 


INDEX. 


535 


Methylhydroxysalicylic  acid,  362 
Methylhypogallic  acid,  498 
Methyl  iodide,  36 
Methyl  isocyanate,  518 
Methylisonoropianic  acid,  508 
Methylisophthalate,  479 
Methyl  isopropylsalicylate,  307 
Methylmetahomoparahydroxybenzoic 

acid,  427 

o-Methylmetahomosalicylic  acid,  424 
Methylmetahydroxybeuzaldehyde,  293 
Methylmetamidobenzoic  acid,  247 
Methylmetatoluidine,  61 
Methyl  nitrite,  578 
Methyl-nitro-isophthalate,  482 
Methylnitrosalicylaldehyde,  292 
Methyl  nitroterephthalate,  489 
Methyl norhemipinic  acid,  514 
Methylnormecouin,  498,  501 
Methylnoropianic  acid,  498,  502 
Methyl  opianate,  505 
Methyl  orsellinate,  432 
/3-Methylorthodihydroxybenzaldehyde, 

348 
o-Methylorthobenzoglycocyamidine, 

243 

£-Methylorthohomometahydroxyben- 
zoic  acid,  426 

Methylorthohomoparahydroxybenzoic 
acid,  427 

Methylorthohomosalicylic  acid,  424 

Methylorthotoluidine,  58 

Methylorthotolylnitrosamine,  58 

Methyl  paradihydroxybenzaldehyde,  349 

Methylparahomosalicylic  acid,  424 

Methylparahydroxybenzaldehyde,  295 

Methylparahydroxybenzoate,   295,  328 

Methylparahydroxybenzoyl      chloride, 
332 

Methyl  paramethoxybenzoate,  330 

Methyl  paratoluate,  419 

Methylparatoluidine,  64 

Methylphthalate,  457 

Methylphthalimidine,  445 

Methylprotocatechuate,  352 

Methylpyrogallic  acid,  53 

Methylpyrogallol,  53 

Methyl pyrogallol  dimethyl  ether,  54 

Methyl  salicylaldehyde,  287 

Methyl  salicylate,  305 

Methyl  salicylic  acid,  305 

Methyl  terephthalate,  484 

Methyl  tetrahydrotcrephthalate,  486 

Methyltoluol,  387 

Methyl  vanillate,  352 

Methylvanillin,  346 

Methyl  veratrate,354 

Monamidobenzoic  acids,  237 

Monethyl  dihydroxy  terephthalate,  517 

Monobromobenzoic  acids,  223 

Monobromoparaxylcnol,  401 

Monobromophthalide,  443 

Monobromorcinol,  41 

Monobromo  toluenes,  10 


Monochlorobenzoic  acids,  217 
Monochlorobenzenyl  trichloride,  196 
Monochlorotoluenes,  8 
Monofluorbenzoic  acids,  226 
Monohydroxy toluenes  and  allied  bodies, 

23    ' 

Mono-iodobenzoic  acids,  225 
Mono-iodorcinol,  41 
Mononitrobenzoic  acids,  229 
Mononitrotoluenes,  13 
Monosulphobenzoic  acids,  268 
Monoxylylamine,  412 
Morintannic  acid,  356 


N. 


NAPHTHALAMIDE,  463 
Naphthalic  acid,  450 
Naphthesic  acid,  450 
Nitradiazobenzoic  acid,  262 
Nitranilic  acid,  520 
e-Nitro-amidobenzamide,  257 
o-Nitvo-amidobenzoic  acid,  256 
£-Nitro-amidobenzoic  acid,  256 
7-Nitro-amidobenzoic  acid,  256 
8-Nitro-amidobenzoic  acid,  256 
e-Nitro-amidobenzoic  acid,  257 
£-Nitro-amidobenzoic  acid,  257 
77-Nitro-amidobenzoic  acid,  257 
Nitro-amidobenzoic  acids,  255 
Nitro-amidosalicylic  acid,  318 
Nitro-anisic  acid,  337 
Nitrobenzinic  acid,  227 
Nitrobenzoene,  4 
Nitrobenzoic  acids,  233 
Nitrobenzylsulphonic  acid,  109 
Nitrococcusic  acid,  425 
Nitro-diamidometaxylene,  409 
Nitro-dimethylmetatoluidine,  62 
Nitro-dracyl,  4 
Nitro-dracy lie  acid,  228 
Nitrogen  bases  of  benzyl,  110 
Nitrogen  compounds  of  benzoyl,  172 
Nitrohemipinic  acid,  511 
Nitro-isophthalic  acid,  482 
Nitromeconin,  500 
Nitro-^-meconin,  501 
Nitrometacresol,  27 

o-Nitrometahydroxybenzaldehyde,  293 
j8-Nitrometahydroxybenzaldehyde,  293 
7-Nitrometahydroxybenzaldehyde,  293 
Nitrometahydroxybenzoic  acids,  323 
o-Nitrometahydroxybenzoic  acid,  324 
)8-Nitrometahydroxybenzoic  acid,  324 
7-Nitrometahydroxybenzoic  acid,  324 
Tj-Nitrometahydroxybenzoic  acid,  324 
Nitrometatoluic  acids,  417 
o-Nitrometaxylene,  396 
s-Nitrometaxylene,  396 
r-Nitrometaxylene,  396 
a-Nitro-a-metaxylidine,  408 
s-Nitro-s-metaxylidine,  408 
v-Nitrol-a-metaxylidine,  408 


536 


INDEX. 


a-Nitro-s-metaxylidine,  408 
Nitromethane,  518 

Nitromethylnoropianylhydrazide,  508 
Nitromethylnoropianic  acid,  503 
Nitromethylnorhemipinic  acid,  514 
Nitro-opianic  aci(l,  507 
Nitro-opianylphenylhydrazide,  508 
a-Nitro-orcinol,  41 
/3-Nitro-orcinol,  41 
a-Nitro-orthocresol,  25 
/8-Nitro-orthocresol,  26,  51 
7-Nitro-orthocresol,  26 
Nitro-orthotoluic  acids,  415 
o-Nitro-orthoxylene,  395 
y-Nitro-orthoxylene,  395 
a-Nitroparaciesol,  30 
0-Nitroparacresol,  30 
Nitroparahydroxybenzoic  acid,  335 
Nitroparahydroxybcnzaldehyde,  296 
a-Nitroparatoluic  acid,  421 
0-Nitroparatoluic  acid,  421 
/8-Nitroparatolunitril,  421 
Nitroparaxylene,  397 
o-Nitroparaxylidine,  408 
jS-Nitroparaxylidine,  408 
7-Nitroparaxylidine,  408 
a-Nitrophthalic  acid,  474 
v-Nitrophthalic  acid,  473 
Nitrophthalic  acids,  473 
a-Nitrophthalicanhydride,  475 
a-Nitro-salicylaldehyde,  292 
/3-Nitrosalicylaldehyde,  292 
Nitrosalicylic  acids,  315 
a-Nitrosalicylic  acid,  315 
/3-Nitrosalicylic  acid,  316 
Nitrosodibenzylamine,  116 
Nitroso-dimethylmetatoluidine,  62 
Nitrosohemipinimidine,  501 
Nitrosomethylmetanitrobenzene,  147 
Nitrosomethylnitrobenzene,  147 
Nitrosomethylparatoluidine,  65 
Nitrosometracresol,  51 
Nitrosoparaxylorcinol,  402 
Nitrosophthalimidine,  444 
Nitro-substitution  products,  41,  293 
Nitro-sub.stitution  products  of  benzoic 

acid,  227 
Nitro-substitution  products  of  toluene, 

13 
Nitre-substitution    products    of     the 

xylenes,  395 

Nitrosulphobenzoic  acids,  275 
Nitroterephthalamide,  489 
Nitro-terephthalaldehyde,  449 
Nitroterephthalaldehydic  acid,  449 
Nitro-terephthalic  acid,  488 
Nitrotolueno,  13 
/3-Nitrotoluene,  15 
Nitrotoluidine,  15 
Nitrotoluidines,  69 
Nitro-uramidobenzoyl,  242 
Nitroxylidines,  408 
Norhemipinic  acid,  498 
Normal  barium  hydroxamate,  208 


Normal  barium  metasulphobenzoate, 

270 

Normal  barium  a-nitrosalicylate,  316 
Normal  barium  /8-nitrosalicylate,  316 
Normal  barium  parasu]phobenzoate,273 
Normal  barium  phthalate,  457 
Normal  calcium  benzamoxalate,  245 
Normal  ethyl  metasulphobenzoate,  270 
Normal  ethyl  a-nitrophthalate,  475 
Nonr.al  ethyl  y-nitrophthalate,  474 
Normal  lead  metasulphobenzoate,  270 
Normal    methyl    sulphinidephthalate, 

478 

Normal  potassium  hemipinate,  510 
Normal  potassium  metasulphobenzoate, 

270 
Normal  potassium  sulphinidephthalate, 

477 

Normal  silver  hemipinate,  510 
Normal     silver     sulphinidephthalate, 

477 
Normal   sodium    dihydroxyterephtha- 

late,  516 
Normeconin,  498 
Noropianic  acid,  498,  502 


0. 


OCTYL  BENZOATE,  162 

Octacetylhelicoidin,  289 

Oil  of  bitter  almonds,  132 

Opianic  acid,  497,  503 

Opianic  anhydride,  505 

Opianoxime  anhydride,  513 

Opianyl,  497 

Opianylphenylhydrazide,  507 

Opianyl  sulphurous  acid,  506 

Opinic  acid,  514 

Orcein,  44 

a-Orcein,  44 

j8-0rcein,  44 

Orcin,  37 

/3-Orcin,  402 

Orcinol,  37,  429  ;  properties,  39 

Orcinol  acetate,  40 

Orcinolazobeuzene,  40 

Orcinol  diethylcarbonate,  40 

Orcinol  dimethyl  ether,  40 

Orcinol  monomethyl  ether,  40 

Orcinol,  substitution  products  of,  41 

Orcylaldehyde,  427 

Orn'ithine,  193 

Ornithuric  acid,  192,  193 

a-Orsellic  acid,  429 

Orsellinic  acid,  432,  438 

a-0rsel!inic  acid,  429 

Orthamidobenzaldoxime,  149 

Orthamidobenzaldehydc,  149 

Orthamidobenzyl  alcohol,  105 

Ortho    -   aldehydometahydroxybenzoie 

acid,  492 
Ortho    -   aldehydoparahydroxybenzoic 

acid,  491 


INDEX. 


537 


Ortho  •  aldehydophenoxyacetic       acid, 

289 

Ortho-aldehydosalicylic  acid,  491 
Ortho-amidobenzamide,  240 
Ortho-amidobenzoic  acid,  237 
Ortho-amidobenzoic   acid,  hydrochlor- 

ide,  239 

Ortho- amidobenzonitril,  240 
Ortho-amidopara-azotoluene,  78 
Ortho -azobenzoic  acid,  265 
Ortho-azotoluene,  75 
Ortho-azoxybenzoic  acid,  265 
Ortho-azoxytoluene,  77 
Orthobenzaraoxalic  acid,  244 
Orthobenzidenephenylhydrazine,  291 
a-Orthobenzocreatinine,  243 
j8-0rtbobenzocreatinine,  244 
Orthobenzoglycocyamidine,  243 
Orthobenzoic  acid,  194 
Orthobenzoylliydrazide,  264 
Orthobeuzyl  thioformate,  106 
Orthobromobenzaldehyde,  145 
Orthobromobenzoic  acid,  223 
Orthobromobenzyl  alcohol,  102 
Orthobromo-benzylamine,  118 
Orthobromobenzyl  bromide,  102 
Orthobromotoluene,  10 
Orthocarbonylphenylphosphoryl    chlo- 
ride, 311 
Orthocarboxylphenylphosphoric     acid, 

311 

Orthochlorobonzaldehyde,  143 
Orthochlorobenzidene  chloride,  143 
Orthochlorobenzoic  acid,  144,  217 
Orthochlorobenzonitril,  218 
Orthochlorobenzoyl  chloride,  218,  462 
Orthochlorocarbonylphenyl  metaphos- 

phate,  311 

Orthochloroparanitrotoluene,  19 
Orthochlorotoluene,  8 
Orthocresol,  24,  25 
Orthocresyl  benzoate,  164 
Orthocresyl  oxide,  25 
Orthocyanobenzoic  acid,  468 
Orthodiazobenzoic  acid  nitrate,  261 
Orthodiazobenzoic     acid     seminitrate, 

261 

Orthodibroino-benzylamine,  119 
o-Orthodihydroxybenzaldehyde,  343 
Orthodihydroxybenzoic  acid,  350 
Orthodinitrotoluene,  17 
Orthofluorbenzoic  acid,  226 
Orthofluorhippuric  acid,  226 
o-Orthohomometahydroxybenzoic  acid, 

426 
/3-Orthohomometahydroxybenzoic  acid, 

426. 
Orthohomoparahydroxybenzaldehyde, 

422 
Or  th  oh  omoparahy  droxybenzoic       acid, 

427 

Orthohomosalicylaldehyde,  422 
Orthohomosalicylic  acid,  424 
Orthohydrazinebenzoic  acid,  264 


Orthohydrazobenzoic  acid,  265 
Orthohydroazotoluene,  75 
Orthohydroxybenzaldehyde,  285 
Orthohydroxybenzidene  acetate,  290 
Orthohydroxybenzidene       compounds, 

290 

Orthohydroxybenzidenoxime,  290 
Orthohydroxybenzoic  acid,  297 
Orthohydroxy benzyl  alcohol,  279 
Orthohydroxybenzyl  ethyl  ether,  280 
Orthohydroxybenzyl  glucoside,  281 
Orthohydroxybenzyl     methyl      ether, 

280 

Orthohydroxymetatolualdehyde,  422 
a-Orthohydroxymetatoluic  acid,  423 
Orthohydroxymetaxylyl  alcohol,  422 
Orthohydroxymethylbenzoic  acid,  442 
Orthohydroxymethylparahydroxyben- 

zoic  acid,  490 

Orthohydroxymethylsalicylic  acid,  490 
Orthohydroxyparatolualdehyde,  422 
Orthohydroxyparatoluic  acid,  424 
Orthohydroxymetatolualdehyd e,  422 
i/-0rthohydroxymetatcluic  acid,  424 
Ortho-iodobenzoic  acid,  225 
Ortho-iodotoluene,  13 
Orthomethoxybenzyl  alcohol,  280 
Orthomethoxyparahydroxybenzalde- 

hyde,  348 

Orthomethyl-j8-resorcylic  acid,  360 
Orthonitrobenzoyl  chloride,  230 
Orthonitrobenzyl  alcohol,  104 
Orthonitrobenzaldehyde,  146,  240 
Orthonitrobenzaldoxime,  146 
Orthonitrobenzoic  acid,  228,  229 
Orthonitrobenzonitril,  230 
Orthonitrobenzyl  chloride,  105 
Orthonitrobenzyl  iodide,  105 
Orthonitrometatolualdehyde,  413 
o-Orthonitrometatoluidine,  70 
£-Orthonitrometatoluidine,  70 
o-Orthonitromethylmetahydroxybenz- 

aldehyde,  294 
j3-0rthonitromethylmetahydroxybenz- 

aldehyde,  294 

a-Orthonitro-orthotoluidine,  69 
£-Orthonitro-orthotoluidine,  69 
Orthonitroparatoluidine,  70 
Orthonitrophthalide,  446 
Orthonitrotoluene,  15 
Orthosulphamidobenzoic  acid,  268 
Orthosulphobenzoic  acid,  268 
Orthothiocresol,  31 
Orthotolualdehyde,  413 
Orthotoluamide,  414 
Orthotoluic  acid,  414 
Orthotoluidine,  57 
Orthotoluidine  hydrobromide,  58 
Orthotoluidine  hydrochloride,  58 
Orthotoluidine  nitrate,  58 
Orthotoluidine  oxalate,  58 
Orthotoluidine  sulphate,  58 
Orthotolunitril,  414 
Orthotoluyl  chloride,  414 


538 


INDEX. 


Orthotoluyl arsenic  acid,  86 
Orthotoluylenediamine,  72 
Orthotolyl  carbamide,  59 
Orthotolyl  isocyanate,  59 
Orthotolyl  mustard  oil,  60 
Orthotolylphosphenilic  acid,  84 
Orthotolylphosphenylons  acid,  84 
Orthotolylphosphorus  dichloride,  84 
Orthotolylstibine,  86 
Orthotolyl  thiocarbamide,  59 
Orthotribromo-benzylamine,  119 
Ortho-uramidobenzoic  acid,  243 
Orthoxylene,  388,  389,  390 
a-Orthoxylenol,  400,  401 
u-Orthoxylenol,  400 
Orthoxylenesulphonamide,  398 
Orthoxylouesulphonic  acid,  398 
Orthoxyienesulphonic  chloride,  398 
Orthoxylidene  tetrachloride,  447 
o-Orthoxylidine,  406 
u-Orthoxylidine,  406 
Orthoxyloquinol,  403 
Orthoxyloquinone,  404 
Orthoxylyl  alcohol,  411 
Orthoxylyl  bromide,  412 
Orthoxylyl  chloride,  412 
Orthoxylylene  acetate,  440 
Orthoxylylene  alcohol,  439 
Orthoxylylene  bromide,  440 
Orthoxylylene  chloride,  439 
Orthoxylylene  ethyl  ether,  439 
Orthoxylylene  iodide,  440 
Orthoxylylene  sulphide,  440 
Orthrin,  128 
Orthylene,  439 
Oxalamidobenzoic  acid,  249 
Oxalanthranilic  acid,  244 
Oxides  of  benzoyl,  166 
Oxybenzonitrisulphuric  acid,  199 
Oxybenzuramic  acid,  250 


P. 


PARA-ACETOBENZYL  ACETATE,  284 
Para-acetoxybenzoic  acid,  330 
Para-  aid  ehy  dome  tahydroxybenzoic 

acid,  492 

Para-aldehydosalicylic  acid,  491 
Para-amidohydroxymethylbenzoic  acid, 

446 

Para-amidopara-azotoluene,  78 
Para-azotoluene,  76 
Parabenzidene  sulphide,  138 
Parabenzophosphenilic  acid,  84 
Parabromobenzaldehyde,  145 
Parabromobenzoic  acid,  224 
Parabromobenzyl  acetate,  102 
Parabromobenzyl  alcohol,  101 
Parabromobenzyl  bromide,  101 
Parabromotoluene,  11 
Paracarbamidobenzoic  acid,  254 


Paracarbonylorthophosphoric  acid,  332 
Paracarbonylphenylphosphoryl      chlor- 
ide, 332 

Parachlorobenzaldehyde,  144 
Parachlorobenzoic  acid,  9,  221 
Parachlorobenzoic  acid,  221 
Parachlorobenzyl  acetate,  101 
Parachlorobenzyl  alcohol,  99,  100 
Parachloro-benzylamine,  118 
Parachlorobenzyl  bromide,  101 
Parachlorobenzyl  chloride,  100 
Parachlorobenzyl  ethyl  ether,  100 
Parachlorobenzyl  hydrosulphide,  106 
Parachlorometacresol  methyl  ether,  32 
Parachlorometatoluene,  19 
Parachlororthonitrotoluene,  1 9 
Parachlorotoluene,  9 
Paracresol,  23,  24,  25,  28 
Paracresyl  benzoate,  164 
Paracresyl  oxide,  28 
Paradiamidobenzylamine,  120 
Paradiazo-amidobenzoic  acid,  263 
Paradiazobenzoic  acid  nitrate,  262 
Paradichloro-benzylamine,  118 
Paradihydroxybenzaldehyde,  349 
Paradihydroxybenzoic  acid,  361 
Paradi-iodo-benzylamine,  118 
Paradinitrobenzylamine,  119 
Para-ethoxybenzoic  acid,  330 
Parafluorhippuric  acid,  227 
Parafluorbenzoic  acid,  226 
Parahomometahydroxybenzoic        acid, 

425 

Parahomosalicylaldehyde,  422 
Parahomosalicylic  acid,  423 
Parahydrazobenzoic  acid,  266 
Parahydrazotoluene,  76 
Parahydroxybenzalclehyde,  294 
Parahydroxybenzaldoxime,  296 
Parahydroxybenzamide,  333 
Parahydroxybenzanilide,  333 
Parahydroxybenzide,  332 
Parahydroxybenzoates,  328 
Parahydroxybenzoic  acid,  108 
Paradroxybenzoic   acid,  326  ;  substitu- 
tion products  of,  334 
Parahydroxybenzonitril,  334 
Parahydroxybenzoylparahydroxy-ben- 

zoic  acid,  331 

Parahydroxybenzoyl  sulphuric  acid,  336 
Parahydrox}  benzuric  acid,  333 
Parahydroxybenzyl  acetate,  284 
Parahydroxy benzyl  alcohol,  283 
Parahydroxybenzyi  methyl  ether,  284 
P.irahydroxybenzyl  thio-carbimide,  284 
Parahydroxymetatoluic  acid,  427 
Parahydroxymetatolualdehyde,  422 
Parahydroxymethylbenzoic  acid,  442 
Parahydroxymcthylsalicylic  acid,  490 
Parahydroxyorthotolualdehyde,  422 
Parahydroxyorthotoluic  acid,  426 
Parahydroxyphenylacetonitril,  284 
Para-iodobenzaldehyde,  146 
Para-iodobenzoic  acid,  225 


INDEX. 


539 


Para-iodobenzyl  alcohol,  102 
Para-iodo-benzylamine,  118 
Para-iodobenzyl  bromide,  102 
Para-iodotoluene,  13 
Paraleucaniline,  148 
ParaleucotoluHine,  77 
Paramethoxybenzoic  acid,  329 
Paramethoxybenzylamine,  284 
Paramethoxybenzyl  chloride,  284 
Paramethyl-#-resorcylic  acid,  360 
Paramethoxysalicylaldehyde,  349 
Paramidobenzaldehyde,  150 
Paramidobenzaldoxime,  150 
Paramidobenzamide,  253 
Paramidobenzanitril,  253 
Paramidobenzoic  acid,  253 
Paramidobenzoic    acid    hydrochloride, 

253 

Paramidobenzylphenylamine,  120 
Paramidodiazobenzoic  acid,  263 
Paramidophthalide,  446 
Paranitrobenzaldehyde,  148 
Paranitrobenzaldoxiine,  149 
Paranitrobenzamide,  232 
Paranitrobenzidene  bromide,  148 
Paranitrobenzidene  chloride,  148 
Parauitrobenzoic  acid,  232 
Paranitrobenzonitril,  233 
Paranitrobenzoyl  chloride,  232 
Paranitrobenzyl  acetate,  104 
Paranitrobenzyl  alcohol,  99,  103 
Paranitrobenzylamines,  119 
Paranitrobeazyl  bromide,  99,  103 
Paranitrobenzyl  chloride,  103 
Paranitrobenzyl  hydrosulphide,  106 
Paranitrobenzyl  iodide,  103 
Paranitrobenzyl  nitrate,  ]  03 
Paranitrobenzyl  oxalate,  104 
Paranitrobenzyl  thiocyanate,  123 
Paranitrobenzylyphenylamine,  119 
Paranitro-diamidotriphenylmethane, 

148 

Paranitrohippuric  acid,  233 
Paranitrohydroxymethylbenzoic    acid, 

446 
Paranitroinethylmetahydroxybenzalde- 

hyde,  294 

Paranitrotoluene,  15,  16 
Paranitro-orthotoluidine,  69 
Paranitrophthalide,  445 
Para-orsellinaldehyde,  427 
Para-orsellinic  acid,  436,  438 
Paraph enoxybenzoic  acid,  331 
Paraphosphorsellinic  acid,  436 
Pararosaniline,  148 
Pararosotoluidine,  77 
Parasulphamidobenzoic  acid,  273 
Parasulphamido-orthotoluic  acid,  416 
Parathiocresol,  31 
Paratolualdehyde,  413 
Paratoluamide,  419 
Paratoluylenediamine,  73 
Paratoluic  acid,  418 
Paratoluidine,  63 


Paratoluidine  hydrobromide,  64 
Paratoluidine  hydrochloride,  64 
Paratoluidine  nitrate,  64 
Paratoluidine  phenate,  64 
Paratoluidine  sulphate,  64 
Paratolunitril,  420 
Paratoluylamido-acetic  acid,  419 
Paratoluyl  chloride,  419 
Paratolylbenzoyl  thio-urea,  179 
Paratolylboron  chloride,  87 
Paratolyl  carbamide,  66 
Paratolylhydrazine,  75 
Paratolyl  mustard  oil,  67 
Paratolylphosphenilic  acid,  83 
Paratolylphosphenylous  acid,  83 
Paratolylphosphine,  84 
Paratolylphosphonium  iodide,  84 
Paratolylphosphorus  dichloride,  83 
Paratolylphosphorus  oxychloride,  83 
Paratolylphosphorus  tetrachloride,  83 
Paratolylsilicic  acid,  87 
Paratolylsilicon  chloride,  87 
Paratolylsilicon  oxide,  87 
Paratolylstibine,  86 
Paratolylstibine  bromide,  86 
Paratolylstibine  chloride,  86 
Paratolylstibine  hydroxide,  86 
Paratolylstibine  iodide,  86 
Paratolylstibine  oxide,  86 
Paratolyl  thiocarbamide,  67 
Paratolyl  thiocarbimides,  67 
Paratolyl  urethane,  67 
Paratriamidobenzylamino,  120 
Paratribromo-benzylamine,  118 
Paratrichloro-benzylamine,  118 
Paratri-iodo-benzylamine,  118 
Paratrinitrobenzylamine,  119 
Para-uramidobenzoic  acid,  254 
Paraxylyl  alcohol,  412 
Paraxylenol,  401 
Paraxylene,  388,  389,  391 
'Paraxylenesulphamide,  399 
Paraxylenesulphonic  acid,  399 
Paraxylenesulphonic  chloride,  399 
Paraxylidine,  407 
Paraxylidene  tetrachloride,  448 
Paraxyloquinol,  403 
Paraxyloquinone,  404 
Paraxylorcinol,  402 
Paraxylylene  acetate,  441 
Paraxylylene  alcohol,  441 
Paraxylyl  bromide,  412 
Paraxylylene  bromide,  441 
Paraxylylene  chloride,  441 
Paraxylylene  iodide,  441 
Paraxylylene  monobenzoate,  442 
Paraxylylene  mono-ethyl  ether,  441 
Paraxylyl  ethyl  ether,  412 
Parazobenzoic  acid,  266 
Penta-acetyltannin,  374 
Pentabromobenzoic  acid,  225 
Pentabromorcinol,  41 
Pentabromotoluene,  12 
Pentachlorobenzidene  chloride,  8,  145 


540 


INDEX. 


Pentachlorobeuzyl  alcohol,  100 
Pentachlorobenzyl  chloride,  101 
Pentachlororcinol,  41 
Pentachlorotoluene,  10 
Pentachloroxyloue,  34 
Persio,  44 
Peruvin,  90 
Petrol,  387 
Phenol,  297 
Phenylacetamide,  113 
Phenylacetonitril,  113 
Phenylaceturic  acid,  186 
Phenylamido-acetonitril,  113 
Phenylbenzaldehydine,  141 
Phenylbenzaldehydine     hydrochloride, 

141 

Phenylbenzenylamidine,  203 
Phenyl  benzoate,  163 
Phenylbenzoyl  thio-urea,  179 
Phenylchlorocarbylethyl  ether,  100 
Phenylchloroform,  195 
Phenylene  benzoate,  164 
Phenylenebenzcnylaraidine,  205 
Phenylenediethylacetone,  462 
Phenylenenitrobenzenylamidine,  206 
Phenylhydrazine     nitro-opianic     acid, 

508 

Phenylhydroxyacetic  acid,  132 
Phenylhydroxyacetonitril,  113,  131 
Phenyl  isophtiialate,  480 
Phenylorthotolylamine,  59 
Phenylmetabenzoglycocyamine,  252 
Phenylraethyl,  89 
Phenyl  methylsalicylate,  308 

Phenylnitro-ethylene,  135 

Phenylorthotolyl  thiocarbamide,  60 

Phenyl  paraphenoxy benzoate,  331 

Phenyl  parahydroxy benzoate,  330 

Phenyl  paratoluate,  419 

Phenylparatoluidine,  65 

Phenylparatolylamine,  65 

Phenylphthalimide,  464 

Phenyl phthalimidine  445 

Phenyl propionic  acid,  186 

Phenylpropionitril,  122 

Phenyl  salicylate,  307 

Phenyl  terephthalate,  484 

Phenylthiobenzamide,  178 

Phenylthiobenzoate,  171 

Phloroglucinol,  357 

Phloroglucinolcarboxylic  acid,  380,  381 

Phlorone,  404 

Phosphorsellinanilide,  433 

Phosphorsellinic  acid,  433 

Phosphorus     compounds     of     benzyl, 
124 

Phosphorus  derivatives  of  toluene,  83 

Phosphorus    pentachloride     and     its 
action  upon  salicylic  acid,  309 

Phospho-salicylic  acid,  309 

Phthalalcohol,  439 

Phthalaldehyde,  442,  447 

Phthalaldehydic  acid,  447 

Phthalamic  acid,  463 


Phthalamil,  464 

Phthalanilic  acid,  464 

Phthaldns,  458 

Phthalic  acid,  439,  451,  452 

Phthalic   acid,    addition    products   of, 

469 
Phthalic    acid,    halogen     substitution 

products  of,  471 
Phthalic  acids,  450 
Phthalic  anhydride,  457  ;  apparatus  for 

the  sublimation  of,  459 
o-Phthalicsulphaniic  acid,  477 
Phthalide,  442,  458 
Phthalide-anil,  445 
Phthalidehydrazide,  445 
Phthalimide,  463 
Phthalimide  oxime,  469 
Phthalimidine,  444 
Phthalinic  acid,  464 
Phthalylacetic  acid,  458 
Phthalyl  chloride,  458 
Phthalyldiamide,  466 
Plithalylhydroxylamine,  466,  468 
Phthalyloxide,  457 
Phthalyl  sulphide,  462 
Picranyl,  129 

Picroerythrin,  429,  431,  434 
Picrorocellin,  436 
Piperonal,  347 
Piperonic  acid,  355 
Piperonyl  alcohol,  347 
Polysalicylnitril,  313 
Pomacese,  131 
Populin,  282,  317 
Potassium  benzidene  sulphite,  137 
Potassium  benzoate,  160 
Potassium  benzylsulphonate,  108 
Potassium  chlorobenzylsulphonate,  108 
Potassium  cyauate,  518 
Potassium  dibenzhydroxamate,  210 
Potassium  dinitroparacresate,  31 
Potassium  dinitrosalicylate,  317 
Potassium  gallate,  368 
Potassium  hemipiiiimide,  513 


Potassium  hippurate,  189 

hydroxyphthala: 
Potassium  isophthalate,  479 


Potassium  hydroxyphthalamate,  467 


Potassium  opianate,  504 

Potassium  parahydroxybcnzoate,  328 

Potassium  phthalimide,  463 

Potassium  piperonate,  356 

Potassium  salicylaldehyde,  287 

Potassium  salicylate,  302 

Potassium  thiobenzoate,  170 

Potassium  o-toluquinonoximate,  51 

Potassium  tribenzarsenate,  278 

Proin,  128 

Propenyl  salicylate,  306 

Propyl  benzoate,  162 

Propylene,  24 

Propylene  benzoate,  163 

Propyl  salicylate,  306 

Propyl  terephthalate,  484 

Protocatechuic  acid,  350,  357 


INDEX. 


541 


Protocatechuicaldehyde,  343 
Protomtrobenzoine,  13 
Pseudoery  tin-in,  428 
Pseudotoiuidine,  55 
Pyrogallocarboxylates,  379 
Pyrogallolcarboxylic  acid,  378,  381 


Q. 


QTJERCIMERIC  acid,  509 
Quinates,  the,  384 
Quinic  acid,  186,  381 
Quinoldicaiboxylic  acid,  515,  518 
Quinonedihydrodicarboxylic  acid,  518 
Quinonoximo  benzoate,  165 


R. 


RESORCINOLPICARBOXYLIC  acid,  515 
0-Resorcylaldehyde,  348 
a-Resorcylic  acid,  358 
/3-Resorcylic  acid,  359,  437 
7-Resorcylic  acid,  360 
Retinaphtha,  3 
Ribbon  Litmus,  46 


S. 


SACCHARIN,  269 

Safranine,  80 

Salicin,  281 

Salicyl,  285 

Salicyl  alcohol,  279 

Salicylaldehyde,  285  ;  properties,  286 

Salicylaldehyde,  substitution  products 

of,  292* 

Salicylaldoxime,  290 
Salicylamide,  312 
Salicylates,  301 
Salicyl  chloraldide,  308 
Salicyl  chloride,  310 
Salicyl  hydride,  285 
Salicylhydroxyacetic  acid,  309 
Salicylic  acid,  108,  157,  297 
Salicylic  acid,  ethereal  salts  of,  306 
Salicylic  acid,  substitution  products 

of,  313 

Salicylic  ethers,  306 
Salicylic  ethers,  ethereal  salts  of,  307 
Salicylide,  308 

Salicyl  monochlorophosphate,  309 
Salicylnitril,  313 
Salicyl parazobenzenesul phonic  acid, 

319 

Salicylsulphuric  acid,  319 
Salicyluric  acid,  312 
Saligesion,  279 
Saliretin,  280 
Salireton,  280 
Salol,  307 
Salts  and  ethers  of  benzoic  acid,  160 


Selenium  compounds  of  benzyl,  109 

Silicon  compounds  of  benzyl,  127 

Silicon  paratolyl,  87 

Silicon  tetrabenzyl,  127 

Silicotetrabenzylmethane,  127 

Silver  benzarsenate,  277 

Silver  benzarsenite,  278 

Silver  benzoate,  161 

Silver  benzophosphinatc,  276 

Silver  hemipinimide,  513 

Silver  hippurate,  190 

Silver  isophthalate,  479 

Silver  metasulphobenzoate,  270 

Silver  methylnoropianate,  503 

Silver  opianite,  504 

Silver  orthohydroxymethylbenzoate, 

442 

Silver  parahydroxybenzoate,  328 
Silver  phthalate,  457 
Silver  phthalimide,  463 
Silver  piperonate,  356 
Silver  quinate,  384 
Silver  salicylate,  304 
Silver  terephthalate,  484 
Sinalbin,  377 
Sinapic  acid,  376 
Sinapin,  375 
Sinapin  thiocjTanate,  375 
Sodium  arsenetribenzoate,  278 
Sodium  benzidene  sulphite,  137 
Sodium  benzoate,  160 
Sodium  gallate,  368 
Sodium  hippurate,  189 
Sodium  metanitrobenzoate,  231 
Sodium  metaxylenesulphonate,  398 
Sodium  orthoxylenesulphonate,  398 
Sodium  parahydroxybenzoate,  328 
Sodium  paraxylenesulphonate,  399 
Sodium  phenylenecarbonate,  299 
Sodium  quinate,  384 
Sodium  salicylate,  302 
Sodium  tetrahydroxyterephthalate,  520 
Sodium  a-toluquinonoxirnate,  51 
Spirasic  acid,  285 
Spiroyl  hydride,  285 
Spiroylous  acid,  285 
Spiroyl wasserstoflsaure,  285 
Strontium  hippurate,  189 
Substitution  products  of  benzyl  alcohol 

and  its  derivatives,  98 
Substitution  products  of  anisic  acid, 

336 
Substitution     products     of    benzidene 

compounds,  143 
Substitution  products  of  benzylamines, 

118 
Substitution    products    of    isophthalic 

acid,  481 
Substitution  products  of  metahydroxy- 

benzoic  acid,  323 
Substitution  products  of  parahydroxy- 

benzoic  acid,  334 
Substitution  products   of  salicyl-alde- 

hyde,  292 


542 


INDEX. 


Substitution  products  of  salicylic  acid, 

313 
Substitution   products   of  terephthalic 

acid,  488 
Substitution  products  of  the  xylenes, 

392 

Sulphamicphthalic  anhydride,  477 
Sulphamidobenzonitril,  272 
o-Sulpharnidouietatoluic  acid,  418 
v-Sulphamidometatoluic  acid,  418 
Sulphamidoparatoluic  acid,  421 
Sulphinidephthalic  acid,  477 
Sulphobenzoic  acid,  20 
Sulphobenzoyl  hydride,  138 
o-Sulpho-isophthalic  acid,  482 
s-Sulpho-isophthalic  acid,  482 
Sulphometahydroxybenzoic  acid,  325 
Sulphoparahydroxybenzoic  acid,  335 
Sulphoparatoluic  acid,  421 
o-Sulphophthalic  acid,  476 
v-Sulphophthalic  acid,  477 
Sulphophthalic  acids,  476 
Sulphorthot,oluic  acid,  415 
Sulphosalicylic  acid,  318 
Sulphoterephthalicacid,  490 
Sulphur  compounds  of  benzoyl,  170 
Sulphur  compounds  of  benzyl,  105 
Symmetric  a-diamido-azotoluene,  79 
Symmetric  /3-diamido-azotoluene,  79 
Symmetric  dibenzyl  thiocarlamide,  124 
Symmetric  dibenzyl  urea,  123 
Symmetric  dinitroparatoluidine,  71 
Symmetric     diphenylbenzenylarnidine, 

203 

Symmetric  ethylbenzoyl  urea,  178 
Symmetric  metadihydroxybenzoic  acid, 

358 


T. 


TANNATES,  374 

Tannic  acid,  365,  371 

Tannin,  371  ;  properties,  373 

Tartrophthalic  acid,  470 

Taurylic  acid,  23 

Telerythrin,  428 

Terephthalaldehyde,  447 

Terephthalaldehydic  acid,  449 

Terephthalamic  acid,  485 

Terephthalamide,  485 

Terephthalic  acid,  451,  483  ;  addition 
products  of,  486  ;  substitution  pro- 
ducts of,  488 

Tereplithalonitril,  435 

Terephthalyl  chloride,  485 

Tetrabromolecanoric  acid,  434 

Tetrabromometaxylene,  394 

Tetrabromomethane,  12 

Tetrabromoparaxylene,  395 

Tetrabiomophthalic  acid,  473 

Tetrabromorthoxylene,  394 

Tetrabromoluenes,  12 

Tetracetylhelicin,  289 


Tetrachlorobenzal  chloride,  8 
Tetrachlorobenzidene  chloiide,  145 
Tetrachlorobenzoic  acid,  222 
Tetrachlorobenzyl  alcohol,  100 
Tetrachlorobenzyl  chloride,  101 
Tetrachlorobenzenyl  trichloride,  196 
Tetrachlorocreocone,  36 
Tetrachloroguaiacone,  36 
Tetrachlorophthalic  acid,  472 
Tetrachlororthoxylene,  393 
Tetrachlorotoluene,  10 
Tetrachlorotoluquinone,  50 
Tetrahydro-isophthalic  acid,  481,  487 
Tetrabydrometaxylene,  391 
Tetrahydrophthalic  acid,  470 
Tetrahydroterephthalic  acid,  486 
Tetrahydrotoluene,  6 
Tetrahydroxyhexhydrobenzoic  acid,  383 
Tctrahydroxyphthalic  acids,  519 
Tetrahydroxy terephthalic  acid,  519 
Tetrasalicyli'de,  308 
Thallium  metahydroxybenzoate,  321 
Thallium  salicylate,  303 
Thiobenzaldine,  140 
Thiobenzamide,  177 
Thiobenzanilide,  178 
Thiobenzoic  acid,  170 
Thiobenzoic  anhydride,  171 
Thiocresolo,  31 

Thiometahydroxybenzoicacid,  325 
Thio-opianic  acid,  507 
ThiophthalicaTdiydride,  462 
Thiotoluidine,  72 
Tolualdehydes,  the,  413 
Tolubenzaldehydine,  142 
Toluene  3  et  sc.q. ,  properties,  5 
Toluene,  amido-derivatives  of,  54 
Toluene,  antimony  derivatives  of,  86 
Toluene,  arsenic  derivatives  of,  84 
Toluene,  azo-derivatives  of,  75 
Toluene,  boron  and  silicon  derivatives 

of,  87 

Toluene,  diazo-derivatives  of,  74 
Toluenedisulphoriic  acids,  22 
o-Tolneiiedisulphonic  acid,  22 
j8-Toluencdisul[>honic  acid,  22 
7-Tolueiiedisulphonic  acid,  22 
Toluene  group,  3 

Toluene,  hydrazine  derivatives  of,  75 
Toluene,  mercury  derivatives  of,  87 
Toluene,  phosphorus  derivatives  of,  83 
Toluenemetasulphonamide,  21 
Tolunemetasulphonic  acid,  21 
Toluenemetasulphonic  chloride,  21 
Toluenemonosulphonic  acids,  20 
Tolucneparasulphonamide,  21 
Tolueneparasul phonic  acid,  21 
Tolueneparasulphonic  chloride,  21 
Toluene-orthrsulphonic  acid,  21 
7-Toluenesulplionic  acid,  22 
Toluenesulphonic  acids,  20 
Tolucnetrisul phonic  acids,  22 
Toluenyl  alcohol,  412 
Toluhydroquinonc,  48 


INDEX. 


543 


Toluic  acids,  414 
Toluidine,  4,  14,  111 
Toluidinedisulphonic  acid,  22 
Toluidines,  54 

Tolui dines,   halogen  substitution  pro- 
ducts of  the,  67 
Toluol,  386 
Toluquinhydrone,  50 
Toluquinol,  48 

Toluquinol  dimethyl  ether,  48 
Toluquinol  monomethyl  ether,  48 
Toluquinone,  49 
o-Toluquinone  chlorimide,  51 
Toluquinone,  substitution  products,  50 
a-Toluquinonoxime,  50 
j8-Toluquinonoxime,  51 
)8-Toluquinonoxime  acetate,  51 
Toluquinonoxime  compounds,  50 
Toluric  acid,  419 
Tolusafranine,  80 
Tolusafranine  hydrochloride,  81 
Tolusafranine  nitrate,  81 
Tolusafranine  picrate,  81 
Toluylene-blue,  82 
Toluylene-red,  82 
Toluylene-violet,  82 
Tolyl,  410 

Tolylarsenic  acid,  85 
Tolylboric  acid,  87 
Tolylenediamines,  72 
Triacetoxymetaxylene,  403 
Triacetylgallic  acid,  370 
Triamido-azobenzoic  acid,  264 
Tri-amidobenzoic  acid,  260 
Triamidometaxylene,  409 
Tribenzhydroxylamine,  207 
Tribenzhydroxylamine,  211 
o-Tribenzhydroxylamine,  212 
j8-Tribenzhy<]roxylamine,  212 
•y-Tribenzhydroxylamine,  212 
Tribenzidenediamine,  139 
Tribenzo-arsenic  acid,  85 
Tribenzoylphloro-glucinol,  164 
Tribenzylamine,  110,  115 
Tribenzylamine,  hydrochloride,  116 
Tribenzylamine  nitrate,  116 
Tribenzylamine  sulphate,  116 
Tribenzylarsine,  126 
Tribenzylarsine  dichloride,  125 
Tribenzylarsine  oxide,  126 
Tribenzarsenic  acid,  278 
Tribenzarsenious  acid,  278 
Tribenzy^arsonium  iodide,  126 
Tribromobenzoic  acids,  225 
a-Tribromometaxylenol,  401 
s-Tribromometaxylenol,  401 
v-Tribromometaxylenol,  401 
Tribromoparaxylenol,  401 
Tribromnphthalic  acid,  473 
Tribroinorcinol,  41 
a-Tribromorthoxylenol,  400 
Tribromotoluencs,  12 
Tribromotoluqmnone,  50 
a-Tilchlorobenzaldehyde,  145 


18-Trichlorobenzaldehyde,  145 
o-Trichlorobenzidene  chloride,  145 
/3-Trichlorobenzidene  chloride,  145 
a-Trichlorobenzoic  acid,  222 
£-Trichlorobenzoic  acid,  222 
7-Trichlorobenzoic  acid,  222 
Trichlorobenzoic  acids,  222 
Trichlorobenzyl  alcohol,  100 
Trichlorobenzyl  chloride,  101 
Trichlorobenzenyl  trichloride,  196 
Trichlorophthalic  acid,  472 
Trichlororcinol,  41 
Trichlororthoxylene,  393 
o-Trichlorotoluene,  10 
/3-Trichlorotoluene,  10 
Trichlorotoluquinone,  50 
Trie  thy  1  benzylammonium  iodide,  116 
Triethylgallic  acid,  369 
Triethylhydroxyquinolcarboxylic  acid, 

380 

Triethylpyrogallolcarboxylic  acid,  379 
Trihydroxybenzoic  acids,  363 
Trihvdroxybenzcic  acids,    constitution 

of,'  381 

Trihydroxymetaxylene,  403 
Trihydroxyphthalic  acids,  519 
Trihydroxytoluenes,  53 
Trihydroxy-xylenes,  403 
Tri-iodorcinol,  41 
Tri-iodosalicylic  acid,  315 
Triketohexhydrobenzene,  518 
Trimethylamido-amsic  acid,  338 
Trimethylamidobenzoic  acid,  248 
Trimethylamidosalicylic  acid,  318 
Trimethyl  anise-betaine,  338 
Trimethylene  benzoate,  163 
Trimethyl  ether,  478 
Trimethylhydroxyquinolcarboxylic 

acid,  380 
Trimethylorthotolylammonium  iodide, 

59 
Trimethylparatolylammonium    iodide, 

65 

Trimethyl phosphobenzobetaine,  276 
Triuitro-amarme,  148 
Trinitrobenzene,  symmetric,  18 
Trinitrobcnzoic  acid,  235 
Trinitrohydrobenzamide,  148 
Trinitrometahydroxybenzoic  acid,  324 
s-Trinitrohydroxytoluic  acid,  425 
Trinitrometacresol,  28 
Trinitrometaxylene,  396 
Trinitroparaxylene,  398 
Trinitrophenyl  benzoate,  164 
Trinitro-orcinol,  42 
Trinitro-orthoxylene,  396 
o-Trinitrotoluene,  17 
j8-Trinitrotoluene,  18 
7- Trinitrotoluene,  18 
Trinitrotoluenes,  17 
Triopianide,  505 
Triparatolylarsine,  85 
Triphenylbenzylphosphonium  chloride, 

125 


544 


INDEX. 


Trisul  phometab  ydroxy  benzoic 

326 

Trixylylamine,  413 
Tuluol,  4 

U. 

UMBELLIO  ACID,  329 
Uramidobenzoic  acid,  249,  252 
TJramidobenzoyl,  242 
Uronitrotoluic  acid,  104 


V. 

VANILLA,  345 
Vanillic  acid,  352 
Vanillic  acid  glucoside,  352 
Vanillin,  344 
Vanillin  glucoside,  347 
Vanillyl  alcohol,  346 
Veratric  acid,  354 
Victoria  yellow,  31 


acid,       Xylenes,  amido-derivatives  of  the,  405 
Xylencs,    diamines   and   triamines   of 

the,  409 
Xylenes,  halogen  substitution  products 

of  the,  392 
Xylenes,  nitro  substitution  products  of 

the,  395 
Xylenes,  substitution  products  of  the, 

392 

Xylenesulphonic  acids,  398 
Xylenols,  399 

Xylidenyl  pentachloride,  447 
Xylidines,  405 
Xylol,  386 

Xyloquinones,  the,  404 
Xyloylamines,  412 
Xylyl,  410 
Xylyl  alcohols,  411 
Xylyl  bromides,  412 
Xylyl  chlorides,  412 
Xylyl  compounds,  410 
Xylylene  alcohols,  439 
Xylylidenediamine,  448 


XANTHAROCELLIN,  436 
Xylene  group,  386 
Xylenes,  390 


Z. 

ZINC  HIPPURATE,  189 
Zinc  phthalate,  458 


THE  END. 


3-3 


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